---
title: "VPS glossary: 42 hosting terms in plain English"
description: "What VPS, KVM, vCPU, steal time, NVMe, IOPS, A record, TTL, SSH key, sudo, systemd, SLA and Tier III mean: 42 hosting and Linux terms in one glossary."
url: https://tihost.io/en/blog/vps-glossary
language: en
section: "Basics"
published: 2026-10-05
updated: 2026-10-05
publisher: Tihost (https://tihost.io)
---

# VPS glossary: 42 hosting terms in plain English

> **In short:** A VPS is a virtual machine with its own OS and root access on a shared physical server, a vCPU is a host CPU thread assigned to that machine, and NVMe is an SSD on the PCIe bus, several times faster than SATA. A 99.9% SLA allows about 43 minutes of downtime per month. Below are 42 such terms grouped into servers, hardware, network, access, Linux and rental terms.

**Key takeaways:**

- VPS and VDS mean the same thing today: a virtual machine with its own OS, its own resources and root access on a shared physical server, most often on the KVM hypervisor.
- A vCPU in a VPS plan is a thread of a physical CPU, not a whole core; steal time (`st` in `top`) shows how much CPU time the hypervisor gave to other machines.
- VPS disk speed is defined by the interface (NVMe is several times faster than a SATA SSD) and by IOPS - read and write operations per second - not just by capacity in gigabytes.
- A 99.9% SLA allows about 43 minutes of downtime per month and 99.99% about 4 minutes; a Tier III data center is designed for 99.982% availability.

## Servers and virtualization

These words appear in the first line of every plan: what exactly you rent and what technology it runs on. A detailed comparison is in [VPS vs VDS vs dedicated server](https://tihost.io/en/blog/vps-vs-vds-vs-dedicated).

**VPS** - A VPS (Virtual Private Server) is a virtual machine on a provider's physical server with its own operating system, its own resources and full root access. It is used for websites, bots, VPNs, databases and any software that needs a server running around the clock.

**VDS** - A VDS (Virtual Dedicated Server) is another name for a VPS. The term once separated full virtualization from containers, but at most hosts today both names mean a KVM virtual machine.

**Dedicated server** - A dedicated server is a physical server rented entirely by one customer. You need one when even the largest VPS is not enough or the task requires special hardware such as a GPU or dozens of disks.

**Shared hosting** - Shared hosting is space for a website on a server shared by hundreds of customers, with no root access and no choice of OS. It suits a simple PHP site; how it differs from a VPS is covered in [shared hosting vs VPS](https://tihost.io/en/blog/shared-hosting-vs-vps).

**Hypervisor** - A hypervisor is software that runs several virtual machines on one physical server and divides its CPU, memory and disks between them. The best-known hypervisors are KVM, Xen, VMware ESXi and Microsoft Hyper-V.

**KVM** - KVM (Kernel-based Virtual Machine) is a hypervisor built into the Linux kernel in which every virtual machine gets its own OS kernel. A KVM server can run any Linux, FreeBSD or Windows, Docker and WireGuard; Tihost VPS run on KVM.

**OpenVZ (container virtualization)** - OpenVZ is container virtualization in which all virtual servers on a host share one Linux kernel. Such a server cannot use its own kernel, load kernel modules or run Windows, and Docker and VPN software may be restricted.

**Overselling** - Overselling is selling virtual servers more CPU time or memory than the host physically has, betting that not all customers load their machines at once. Heavy CPU overselling raises steal time, and the server runs slower than advertised.

## Hardware: CPU, memory, disks

The numbers on a plan card - vCPU, gigabytes of memory and disk type - describe the machine's resources. How much of each a given task needs is covered in [how much RAM a VPS needs](https://tihost.io/en/blog/how-much-ram-vps).

**vCPU** - A vCPU (virtual CPU) is a thread of a physical processor that the hypervisor assigns to a virtual machine. The server's OS sees as many processors as the plan has vCPUs, and their speed depends on the host CPU model - at Tihost that is the [AMD Ryzen 9 5950X and 9950X](https://tihost.io/en/blog/amd-ryzen-9-5950x-vs-9950x).

**Steal time** - Steal time (st) is the share of time a virtual machine is ready to work but the hypervisor gives the physical CPU to other machines. It shows in the `st` column of `top` and `vmstat`; if it stays at several percent or more under load, the host does not have enough CPU for everyone. How to test a server yourself is in [VPS benchmark](https://tihost.io/en/blog/vps-benchmark).

**RAM** - RAM (random-access memory) is the fast memory where running programs, caches and databases live. When it runs short, Linux starts using swap, and when it runs out completely, it kills processes (the OOM killer).

**Swap** - Swap is a partition or file on disk where the Linux kernel moves rarely used memory pages when RAM runs out. Swap saves processes from being killed suddenly but is many times slower than RAM; small VPS usually get a 1-2 GB swap file (see [first server setup](https://tihost.io/en/blog/vps-first-setup)).

**NVMe** - NVMe (NVM Express) is a protocol that connects an SSD directly to the PCIe bus, bypassing the SATA interface. NVMe drives deliver several times more operations per second and lower latency than SATA SSDs; every Tihost plan uses NVMe. A comparison is in [NVMe vs SSD](https://tihost.io/en/blog/nvme-vs-ssd).

**SSD** - An SSD (solid-state drive) is flash storage with no moving parts. In hosting descriptions, a plain «SSD» usually means a drive on the SATA interface, whose speed is capped at roughly 550-600 MB/s.

**IOPS** - IOPS (input/output operations per second) is the number of reads or writes a disk completes per second, usually in small 4 KB blocks. For databases and websites IOPS matters more than sequential speed in MB/s; it is measured with the `fio` tool.

## Network and domains

These terms are what makes a server reachable by your site's name and helps it survive a traffic spike. A step-by-step guide is in [how to point a domain to a VPS](https://tihost.io/en/blog/domain-to-vps).

**IPv4** - IPv4 is a 32-bit address such as 203.0.113.10 at which a server is reachable on the internet. Almost no free IPv4 addresses are left in the world, so hosts treat them as a scarce resource; every Tihost VPS gets a public IPv4 address, which you can change once for free from the panel or the bot.

**IPv6** - IPv6 is a 128-bit address such as 2001:db8::1, created to replace IPv4 because of the address shortage. IPv4 and IPv6 are separate protocols: a site reachable only over IPv6 will not open for a user without IPv6 connectivity.

**DNS** - DNS (Domain Name System) is the system that translates a domain name such as example.com into a server's IP address. A domain's DNS records live at the registrar or DNS provider, not on the VPS itself.

**A record** - An A record is a DNS record that maps a domain name to an IPv4 address. For a site to load from a VPS, the domain needs an A record with the server's IP; an IPv6 address uses an AAAA record.

**TTL** - TTL (time to live) in DNS is the number of seconds resolvers and browsers may cache an answer. With a TTL of 3600, a new A record reaches some users only after an hour, so before moving a server the TTL is lowered in advance, for example to 300.

**Reverse proxy** - A reverse proxy is a server, usually nginx or Caddy, that accepts requests from the internet on ports 80 and 443 and forwards them to applications inside the VPS. It also serves the HTTPS certificate and lets several sites share one IP; setup is in [nginx and HTTPS with Let's Encrypt](https://tihost.io/en/blog/nginx-letsencrypt-https).

**CDN** - A CDN (content delivery network) is a network of servers in many countries that caches a site's images, scripts and other static files and serves them from the point closest to the visitor. A CDN takes load off the VPS and speeds the site up for distant users.

**Port** - A port is a number from 1 to 65535 that lets the system tell network services on one IP address apart. Standard ports: 22 for SSH, 80 for HTTP, 443 for HTTPS, 3389 for RDP.

**DDoS** - A DDoS (distributed denial of service) attack is an attempt to take a server down with a flood of requests or traffic from thousands of infected devices at once. Only filtering at the provider's network level stops large attacks; at Tihost that protection is included in the price of every server.

## Access and security

How to get into a server and how to keep strangers out. The full checklist after purchase is in [VPS first setup](https://tihost.io/en/blog/vps-first-setup).

**SSH** - SSH (Secure Shell) is an encrypted protocol for managing a server remotely from the command line; by default it runs on port 22. Connect from a terminal with `ssh root@IP-address`; details are in [how to connect to a VPS over SSH](https://tihost.io/en/blog/ssh-connect-to-vps).

**SSH key** - An SSH key is a pair of files for logging in without a password: the private key stays on your computer and the public key goes to the server in `~/.ssh/authorized_keys`. A key cannot be brute-forced like a password; create one with `ssh-keygen -t ed25519`.

**root** - root is the Linux superuser with unlimited rights: it can install any program, change any file and delete the system. On a Windows server the Administrator account plays the same role.

**sudo** - sudo is a Linux command that runs a single command with root rights on behalf of a regular user, for example `sudo apt update`. Working through sudo is safer than logging in as root: every elevated action is deliberate and lands in the log.

**Firewall (UFW)** - A firewall is a filter for network connections that lets only allowed ports through. On Ubuntu and Debian the easiest one to set up is UFW (Uncomplicated Firewall): first `ufw allow OpenSSH`, then `ufw enable`.

**fail2ban** - fail2ban is a program that reads login logs and temporarily blocks IP addresses after several failed attempts. It is most often installed against SSH password guessing.

**RDP** - RDP (Remote Desktop Protocol) is Microsoft's protocol for connecting to a Windows server's desktop; by default it uses port 3389. The client is built into Windows, while macOS and phones use the Windows App; see [how to connect to a Windows VPS over RDP](https://tihost.io/en/blog/windows-vps-rdp).

**VNC console** - A VNC console is access to a server's screen through the hosting panel, bypassing the server's own network. It works even when SSH or RDP is unreachable, for example after a firewall mistake; at Tihost the console opens in the browser from the panel for a powered-on server.

## Linux and administration

Words that show up in every server setup guide. Which distribution to choose is covered in [Ubuntu vs Debian for a server](https://tihost.io/en/blog/ubuntu-vs-debian-server).

**Linux distribution** - A Linux distribution is a ready-made operating system built on the Linux kernel with a package manager and a set of programs, for example Ubuntu, Debian, AlmaLinux or Rocky Linux. Distributions differ in support period, package freshness and install commands (`apt` on Ubuntu and Debian, `dnf` on AlmaLinux and Rocky Linux).

**LTS** - LTS (Long Term Support) is an OS release with an extended period of security updates. Ubuntu LTS comes out every two years (22.04, 24.04) and gets 5 years of standard updates, which is why servers run LTS releases.

**systemd** - systemd is the init system and service manager in Ubuntu, Debian and most modern distributions: it starts services at boot, restarts crashed ones and collects their logs. The main commands are `systemctl status`, `systemctl restart` and `journalctl -u service-name`.

**cron** - cron is the Linux scheduler that runs commands on a schedule; jobs are edited with `crontab -e`. The line `0 3 * * *` means «every day at 03:00» - a typical time to run [backups](https://tihost.io/en/blog/vps-backup).

**Docker** - Docker is a platform for running applications in containers: an application and all its dependencies are packed into an image that runs the same on any server. Several related containers are described in a `compose.yaml` file; installation is in [Docker on Ubuntu and Debian](https://tihost.io/en/blog/install-docker-ubuntu-debian).

**Container** - A container is an isolated process with its own filesystem, network and resource limits that uses the host system's kernel. Unlike a virtual machine with its own kernel, a container starts in seconds and spends no memory on a separate OS.

## Payment, guarantees and terms

Terms from the contract and the pricing page: what a provider promises and what it asks of the customer.

**SLA** - An SLA (Service Level Agreement) is a commitment to a level of service: a guaranteed availability percentage and compensation if the provider misses it. A 99.9% SLA allows about 43 minutes of downtime per month; Tihost has a 99.9% SLA with compensation for downtime caused by Tihost.

**Uptime** - Uptime is the time a server or service is available, usually as a percentage per month or year: 99.9% is about 8.8 hours of downtime a year, 99.99% about 53 minutes. In Linux, `uptime` is also a command that shows how long the server has run since the last reboot; Tihost statistics per site are on the [status page](https://tihost.io/uptime).

**Tier III** - Tier III is a data center reliability level in the Uptime Institute classification: power and cooling are redundant, and any equipment can be serviced without shutting servers down. Tier III is designed for 99.982% availability; Tihost data centers in Germany, Finland and Poland are Tier III.

**KYC** - KYC (Know Your Customer) is a check of a customer's identity documents before providing a service. Signing up for Tihost needs no KYC: an email, a Google account or Telegram is enough.

**Launch a server in 2 minutes.** AMD Ryzen 9, NVMe and DDoS protection in Germany, Finland and Poland. Pay with crypto or card. [Order a Server](https://tihost.io/login)

## FAQ

### What is the difference between a VPS and a VDS?

Today there is none: at most hosts VPS and VDS mean the same KVM virtual machine with its own OS and root access. In the past, VPS often meant OpenVZ containers without their own kernel.

### What does vCPU mean in a VPS plan?

A vCPU is a physical CPU thread assigned to a virtual machine. A server with 2 vCPUs sees two processors, and their real speed depends on the host CPU model and on how busy the host is with neighbors.

### Which is better for a VPS - SSD or NVMe?

NVMe: it is also an SSD, but connected over the PCIe bus rather than SATA, so it completes several times more read and write operations per second (IOPS). The difference shows most on databases and sites with many small disk requests.

### What is root access on a VPS?

Root access means Linux superuser rights: you can install any software, change kernel and network settings and create users. On a Windows server the equivalent of root is the Administrator account.

### How much downtime does a 99.9% SLA allow?

A 99.9% SLA allows about 43 minutes of downtime in a 30-day month, or roughly 8.8 hours a year. A 99.99% SLA allows about 4 minutes a month.

### How do I get into a VPS when SSH does not respond?

Use the VNC console in the hosting panel: it shows the server's screen bypassing its network, so it works even when the firewall blocks port 22 or the network config is broken. In the console you can log in as root and fix the mistake.

---

Updated 2026-10-05 · https://tihost.io/en/blog/vps-glossary