What Is a CDN? A CDN (Content Delivery Network) is a worldwide network of servers that stores copies of your site's files and serves them from a location close to each visitor. It matters because distance affects s...

What Is Caching? Caching means temporarily storing a ready-made copy of something so it can be served again quickly, instead of rebuilding it from scratch every single time it is requested. It matters because it ma...

What Is an SDK? An SDK (Software Development Kit) is a bundle of tools, code and instructions that a company provides to make it easier for developers to build on top of their platform or service. It matters becaus...

What Is SSL/TLS? SSL/TLS is the technology that encrypts the connection between a visitor's browser and your website. It is what puts the padlock in the address bar and the "s" in https. It matters bec...

What Is a Bug? A bug is a flaw in software that makes it behave differently from how it should — anything from a button that does nothing to a calculation that comes out wrong. It matters because bugs are a normal,...

What Is a Headless CMS? A headless CMS stores and manages your content but, unlike a traditional CMS, does not control how it is displayed. It delivers content through an API to wherever you need it. It matters bec...

What Is DNS? DNS (Domain Name System) is the internet's address book. It translates the human-friendly domain you type — such as progressiverobot.com — into the numerical address computers use to find the rig...

What Is Refactoring? Refactoring means improving the internal structure of code without changing what it does on the outside. The product behaves the same, but the code becomes cleaner and easier to work with. It m...

What Is a Database? A database is an organised store for your information — customers, orders, products, bookings and more — designed so that data can be found, updated and related to other data quickly and reliably. ...

What Is Uptime? Uptime is the proportion of time your website or application is up and available to visitors. It is usually quoted as a percentage, such as 99.9%. It matters because every minute of downtime can mea...

What Is Responsive Design? Responsive design means building a website so it automatically adjusts its layout to look and work well on any screen size — phone, tablet, laptop or large monitor. It matters because mos...

What Is SEO? SEO (Search Engine Optimisation) is the practice of improving your website so it appears higher in search results when people look for what you offer. It matters because most journeys begin with a sear...

What Is a Cookie? A cookie is a small piece of information a website stores in your browser so it can remember things between visits — such as keeping you logged in or holding items in a basket. It matters because ...

What Is a Repository? A repository (often shortened to "repo") is the central, organised home for all the code in a project, together with its full history of changes. It matters because it is the single source of ...

What Is UX and UI? UX (User Experience) is about how easy and pleasant something is to use, while UI (User Interface) is about how it looks — the buttons, colours, layout and typography people see. ...

What Is Version Control? Version control is a system that records every change made to a project's code over time, so you can see the full history, compare versions and roll back if something goes wrong. It matters...

What Is a Progressive Web App? A Progressive Web App (PWA) is a website built to behave like a mobile app — it can be added to a phone's home screen, work offline and send notifications — without needing an app store....

What Is a CMS? A CMS (Content Management System) is software that lets you create and edit the content on your website — text, images, pages and blog posts — without needing a developer for every change. It matters...

What Is CSS? CSS (Cascading Style Sheets) is the language that controls how a web page looks — the colours, fonts, spacing, layout and the way things move or change on hover. It matters because CSS is what turns a ...

What Is the Cloud? The cloud simply means computing power, storage and software that run on someone else's managed servers and are accessed over the internet, rather than on a machine in your own office. It matters...

What Is a Web Application? A web application is software you use through a browser that does real work — such as online banking, a booking system or a project tool — rather than just presenting information like a brochure...

What Is a Webhook? A webhook is an automatic message one system sends to another the moment something happens — for example, notifying your site immediately when a payment is received. It matters because it replace...

What Is Open Source? Open source software is software whose code is published openly, free for anyone to use, inspect, improve and share, usually under a licence that sets out how it may be used. It matters because...

What Is an API? An API (Application Programming Interface) is a defined way for two pieces of software to talk to each other and exchange information, without either needing to know how the other works inside. It m...

What Is JavaScript? JavaScript is the programming language that makes web pages interactive. When something happens without the page reloading — a menu opens, a form validates, a chart updates — JavaScript is usually behi...

What Is Technical Debt? Technical debt is the future cost of taking shortcuts today. When something is built quickly rather than thoroughly, it works now but becomes harder and more expensive to change later. It ma...

What Is Bandwidth? Bandwidth is the amount of data that can travel across a connection in a given time — think of it as the width of the pipe carrying information to and from your site. It matters because limited b...

What Is HTTPS? HTTPS is the secure version of the protocol browsers use to load web pages. The "s" stands for secure, and it means the connection between visitor and site is encrypted. It matters because it keeps i...

What Is a Server? A server is a computer whose job is to store your website or application and send it out to visitors when they request it. It runs around the clock so your site is available whenever someone visits. ...

What Is Latency? Latency is the delay between asking for something online and starting to receive it — the lag before a page or response begins to arrive. It matters because even small delays add up and make a site...

What Is a Framework? A framework is a tried-and-tested foundation of ready-made code and structure that developers build on top of, rather than writing everything from the ground up. It matters because frameworks s...

What Is an Algorithm? An algorithm is simply a precise set of steps for getting something done — a recipe a computer follows to solve a problem or make a decision. It matters because algorithms sit behind almost ev...

What Is Machine Learning? Machine learning is a type of artificial intelligence where software learns patterns from examples and data, rather than being given explicit rules for every situation. It matters because ...

What Is Full-Stack? Full-stack describes work — or a developer — that covers both the front-end (what users see) and the back-end (the server, database and logic) of an application. It matters because a full-stack ...

What Is OAuth? OAuth is the technology that lets you grant one app limited access to your account on another — like "Sign in with Google" — without ever sharing your password. It matters because it makes connecting...

What Is a Front-End? The front-end is the part of a website or app that visitors see and interact with directly in their browser — the pages, buttons, forms, images and animations. It matters because it shapes firs...

What Is a Back-End? The back-end is the part of a system that runs on the server, out of sight — the databases, business logic and integrations that store your data and make everything work. It matters because it i...

What Is a Container? A container is a neat, self-contained package that bundles an application together with everything it needs to run, so it behaves the same on any machine. It matters because containers solve th...

What Is a Static Site? A static site is a website made of pre-built pages that are served exactly as they are, without generating anything fresh from a database on each visit. It matters because static sites are ex...

What Is HTML? HTML (HyperText Markup Language) is the language used to describe the structure of every web page. It tells the browser what is a heading, what is a paragraph, where an image goes and which words are a link....