Every term on this site, explained in plain English.

API

Short for Application Programming Interface. A defined way for two pieces of software to talk to each other, for example, letting one app request data from another over the internet.

Apache

A widely used piece of software that runs on a server and serves web pages to visitors' browsers. One of the two most common web servers, alongside Nginx.

Backup

A separate copy of your data, kept somewhere other than the original, so you can recover it if the original is lost, corrupted, or compromised. A backup you've never tested restoring from isn't a reliable backup.

Bandwidth

The amount of data that can move in and out of your server over a given period. Running low on bandwidth can slow a site down or, on some hosting plans, incur extra charges.

CDN (Content Delivery Network)

A network of servers spread across different locations that cache copies of your website, so visitors load it from a server physically closer to them, making the site feel faster.

Certificate (SSL/TLS)

A small file that proves a website is who it claims to be and enables the padlock and "https" in a browser's address bar, encrypting traffic between the visitor and the server.

CNAME record

A type of DNS record that points one domain name to another, rather than directly to an IP address. Commonly used to point a subdomain like "blog.example.com" at another service.

Container

A lightweight, self-contained package of software and everything it needs to run, kept isolated from other software on the same machine. Docker is the most common tool for building and running containers.

Cron job

A scheduled task on a Linux server that runs automatically at set times, for example, running a backup script every night at 2am without anyone having to trigger it manually.

DNS (Domain Name System)

The system that translates a human-readable domain name like "techster.uk" into the numeric IP address computers actually use to find a server. Often described as the internet's phone book.

Docker

A tool for building, running, and managing containers. Lets you package an application so it runs the same way regardless of the underlying server it's deployed on.

Domain

The human-readable address of a website, such as "techster.uk". Registered through a domain registrar and pointed at a server using DNS.

Encryption

The process of scrambling data so only someone with the correct key can read it. Almost everything on this site touches encryption somewhere, from the HTTPS certificate on a website to the SSH key pair used to log into a server.

Fail2ban

A piece of software that watches a server's logs for repeated failed login attempts and automatically blocks the offending IP address for a period of time, a common defence against automated attacks.

Firewall

A layer of security that controls which network traffic is allowed in or out of a server, based on rules you configure. A properly configured firewall closes every door except the ones you actually need open.

GDPR (General Data Protection Regulation)

An EU law governing how personal data is collected, stored, and processed. Relevant if your server holds data about identifiable people in the EU or UK, regardless of where the server itself is physically located.

GPG key

A cryptographic key used to sign or verify the authenticity of a file, most often seen when adding a new software repository to a server. Checking a GPG signature confirms the software you are installing actually came from the source it claims to.

Hardening

The process of configuring a system to reduce its attack surface, disabling unnecessary services, tightening permissions, enforcing strong authentication, so there are fewer ways for something to go wrong.

HTTPS

The secure version of HTTP, the protocol browsers use to load websites. The "S" means traffic between the visitor and the server is encrypted, using an SSL/TLS certificate.

IP address

A numeric address (like 192.0.2.1) that identifies a specific device or server on a network. DNS exists largely to let humans use domain names instead of remembering these.

Kernel

The core part of an operating system that manages hardware, memory, and running processes. On Linux, the kernel is updated separately from regular software packages, which is why a server sometimes needs a reboot after a routine update to start using the new one.

Latency

The delay between a request being sent and a response arriving. Lower latency means a site or service feels more responsive.

Let's Encrypt

A free, widely used certificate authority that issues SSL/TLS certificates automatically, usually via a client tool like Certbot. It is the reason most small sites and self-hosted services can run over HTTPS without paying for a certificate.

Linux distribution

A specific packaged version of the Linux operating system, such as Ubuntu or Debian. Most VPS servers run some Linux distribution rather than Windows.

Load balancer

A system that spreads incoming traffic across multiple servers, so no single server gets overwhelmed and the whole setup can handle more visitors reliably.

LTS (Long Term Support)

A release of a Linux distribution that receives security updates and bug fixes for a much longer period than a standard release, often five years or more. Production servers should almost always run an LTS release rather than the newest, shortest-lived version.

Malware

Any software designed to cause harm, steal data, or gain unauthorised access, a general term covering viruses, ransomware, spyware, and similar threats.

MX record

A type of DNS record that tells the internet which server handles email for a domain. If this is misconfigured, email for that domain can silently fail to arrive.

Nginx

Pronounced "engine-x". A widely used web server and reverse proxy, known for handling many simultaneous visitors efficiently. The other most common choice alongside Apache.

NVMe

A fast type of solid-state storage, noticeably quicker than older SSDs for the small, random read and write operations a busy server does constantly. Most modern VPS plans use NVMe storage by default.

Open source

Software whose underlying code is publicly available for anyone to read, use, modify, and redistribute, usually under a specific licence. See our full software directory for examples.

Package manager

A tool built into a Linux distribution that installs, updates, and removes software in a consistent, tracked way, rather than manually downloading and configuring everything by hand.

Passphrase

A longer, often multi-word password used to protect something particularly sensitive, such as an SSH private key or a password manager vault. Length matters more than complexity here: a long, random passphrase is both harder to crack and easier to type correctly than a short one full of substituted characters.

Patch

An update to a piece of software, often released specifically to fix a security vulnerability. Applying patches promptly is one of the simplest, highest-impact things you can do for server security.

Phishing

An attempt to trick someone into revealing credentials or sensitive information, usually via a message or website designed to look legitimate. No amount of server hardening protects against a convincing phishing email.

Port

A numbered "channel" on a server that a specific service listens on, for example, web traffic typically uses port 443 (HTTPS) and SSH typically uses port 22. Firewalls control access at the port level.

Public/private key pair

Two mathematically linked keys used for secure authentication. The private key stays secret on your own device; the public key is shared with a server to prove your identity without ever transmitting a password.

Redirect

An instruction that automatically sends a visitor from one URL to another, most commonly used to send HTTP traffic to the encrypted HTTPS version of a site. Configured at the web server level, for example in an Apache virtual host.

Reverse proxy

A server that sits in front of one or more other servers, forwarding incoming requests to the right place. Often used to handle SSL certificates and routing in one central spot rather than in every individual application.

Root access

The highest level of administrative control on a Linux server, able to make any change to the system. Powerful, and correspondingly risky if credentials for it are ever compromised.

SaaS (Software as a Service)

Software you access over the internet and pay for on a subscription, rather than installing and running it yourself, for example Google Workspace or Slack. Most of what this site recommends is the opposite of SaaS: self-hosted alternatives you run and control on your own server.

Self-hosted

Software you run yourself on your own server, rather than using someone else's cloud version of it. The core idea behind most of what this site recommends.

SSH (Secure Shell)

The standard way to securely connect to and control a remote Linux server from your own computer, typically using a key pair rather than a password.

sudo

A command on Linux that lets an authorised user run a specific command with administrative (root) privileges, without being permanently logged in as root.

systemd

The system and service manager used by most modern Linux distributions to start, stop, and monitor background services. Commands like "systemctl restart apache2" are talking to systemd.

Terminal

A text-based window for typing commands directly to a computer's operating system, rather than clicking through a graphical interface. Almost everything involved in setting up and hardening a VPS happens in a terminal, usually connected to the server over SSH.

Two-factor authentication (2FA)

A login method requiring a second proof of identity beyond a password, usually a code from an app or a physical key. Significantly reduces the damage a leaked password alone can do.

UFW (Uncomplicated Firewall)

A simplified, beginner-friendly interface for configuring Linux's underlying firewall rules. Most of the training guides on this site use UFW to control which ports are open on a server.

Unattended upgrades

A setting that lets a Linux server install security patches automatically, without someone logging in to trigger them by hand. Reduces the window between a vulnerability being disclosed and a server actually being patched against it.

Uptime

The proportion of time a server or service is up and reachable, usually expressed as a percentage. No configuration can promise 100% uptime forever; it's a target to work toward, not a guarantee.

Virtual host

A configuration block that lets a single web server handle multiple websites or domains, each with its own settings, from one Apache or Nginx installation. Most self-hosted setups end up running several virtual hosts side by side on the same server.

VPN (Virtual Private Network)

A way of creating a secure, encrypted connection to a private network over the public internet, commonly used to reach internal services remotely without exposing them directly.

VPS (Virtual Private Server)

A virtual machine rented from a hosting provider that behaves like your own dedicated server, with full control over its software, at a fraction of the cost of physical hardware. The foundation of almost everything on this site.

Vulnerability

A weakness in software or configuration that could be exploited to cause harm or gain unauthorised access. Discovering one isn't itself a crisis; leaving it unpatched after discovery is.

WireGuard

A modern VPN protocol known for being fast, simple to configure, and lightweight compared to older alternatives. Commonly used to reach a home network or internal services securely from outside.