Quick answer: This web development glossary explains the terms you are most likely to hear from developers and agencies, grouped by topic: how websites are built, where they live, how they are launched and maintained, and how projects are run. You do not need to become technical. Knowing what these words mean helps you read proposals, ask sharper questions and spot when something important is missing.
How to use this glossary
Skim the headings to find the area you need. Each term has a short definition and, where useful, why it matters to you as the person paying for or running the site. If a term in a proposal is not here and nobody can explain it simply, ask until they do.
Building blocks of a website
Front end: Everything visitors see and interact with in their browser: layout, text, images, buttons and animations. Built with HTML, CSS and JavaScript. Our guide to front end vs back end covers the split in more depth.
Back end: The parts visitors do not see: the server, the application code and the database that store and process information, such as orders, user accounts and form submissions.
Full stack: A developer who works on both front end and back end.
HTML: The language that structures content on a web page: headings, paragraphs, links, images and forms.
CSS: The language that controls how HTML looks: colors, fonts, spacing and layout.
JavaScript: The programming language that runs in the browser and makes pages interactive, such as menus, sliders, form validation and live updates.
Database: Where a website stores structured information like products, posts and customer records. MySQL and SQL Server are common examples.
Framework: A ready-made foundation of code that speeds up development by handling common tasks. Laravel, ASP.NET Core and React are examples.
Library: A collection of reusable code for a specific job, such as jQuery for working with page elements.
API (Application Programming Interface): A defined way for two pieces of software to talk to each other. When your website shows shipping rates from a courier or sends leads to your CRM, an API is usually involved. Our explainer on what an API is goes further.
Integration: Connecting your website to another system, such as accounting, CRM, email marketing or inventory, usually through an API.
Content management
CMS (Content Management System): Software that lets non-developers add and edit pages, posts and media without touching code. WordPress is the most widely used.
Theme: In a CMS, the design layer that controls how content looks.
Plugin or extension: An add-on that adds features to a CMS, such as forms, SEO tools or ecommerce.
Page builder: A drag-and-drop tool for designing pages visually inside a CMS. Convenient, but some add weight that slows pages down.
Headless CMS: A CMS that stores and manages content but does not control how it is displayed. A separate front end fetches content through an API. Our article on headless CMS explains when that makes sense.
Custom post type: A way to add new content types beyond pages and posts, such as case studies, team members or properties.
Design and user experience
UX (User Experience): How easy and pleasant a site is to use, from finding information to completing a purchase.
UI (User Interface): The visual elements people interact with: buttons, forms, menus and icons.
Wireframe: A simple sketch of a page layout showing where content and features go, without final design details.
Mockup: A static, detailed visual of how a page will look.
Prototype: A clickable model of the site used to test layout and flow before development.
Responsive design: A layout that adapts to screen size, so the same site works on phones, tablets and desktops.
Mobile-first: Designing for small screens first, then expanding for larger ones.
Accessibility: Making a site usable for people with disabilities, including those using screen readers or keyboards only. Usually measured against WCAG (Web Content Accessibility Guidelines).
Above the fold: The part of a page visible without scrolling.
CTA (Call to Action): A button or link asking the visitor to do something, like “Book a call” or “Get a quote.”
Hosting and infrastructure
Domain name: Your website’s address, such as example.com.
DNS (Domain Name System): The system that translates a domain name into the server address where the site lives. DNS records also control where your email goes.
Hosting: The service that stores your website’s files and database on a server connected to the internet.
Shared hosting: Many sites on one server sharing its resources. Cheap, but performance can suffer from neighbors.
VPS (Virtual Private Server): A slice of a server with dedicated resources. More control and consistency than shared hosting.
Cloud hosting: Hosting on infrastructure from providers like AWS or Azure, which can scale resources up or down.
SSL/TLS certificate: Enables encrypted HTTPS connections, shown by the padlock in the browser. Required for any site that collects data, and expected for every site.
CDN (Content Delivery Network): A network of servers around the world that store copies of your files closer to visitors to speed up loading.
Uptime: The percentage of time your site is available. Hosts often promise 99.9 percent.
Backup: A copy of your site’s files and database that can be restored if something goes wrong. Ask where backups are stored and how often they are tested.
Performance
Page speed: How quickly a page loads and becomes usable.
Caching: Storing ready-made copies of pages or data so they can be served faster.
Minification: Removing unnecessary characters from code files to make them smaller.
Lazy loading: Loading images and videos only when they are about to appear on screen.
Core Web Vitals: A set of three user experience measures Google introduced in 2020: loading (Largest Contentful Paint), interactivity (First Input Delay) and visual stability (Cumulative Layout Shift). Google has said they will become part of its ranking signals in 2021.
Building, launching and maintaining
Development environment: Where developers write and test code, often on their own computers.
Staging: A private copy of your site used to test changes before they go live.
Production: The live site visitors use.
Deployment: Moving code and changes from development or staging to production. Our guide to the website deployment process explains how good teams do this safely.
Version control: A system that records every change to code, so you can see who changed what and roll back mistakes. Git is the most common. See our article on website version control.
Repository: The storage location for a project’s code and its history, often hosted on GitHub, GitLab or Bitbucket.
Bug: An error that makes the site behave in an unintended way.
QA (Quality Assurance): Testing to find bugs before launch or release.
Browser compatibility: Making sure the site works across browsers like Chrome, Safari, Firefox and Edge.
301 redirect: A permanent redirect from one URL to another. Essential when pages move, to keep visitors and search rankings.
404 error: The “page not found” response when a URL does not exist.
Maintenance: Ongoing updates, security patches, backups and fixes after launch.
SEO terms you will hear from developers
SEO (Search Engine Optimization): Work that helps a site appear in search results for relevant queries.
XML sitemap: A file listing the pages you want search engines to find.
Robots.txt: A file telling search engine crawlers which parts of a site they may crawl.
Meta title and description: The page title and summary that often appear in search results.
Schema markup: Code that describes your content to search engines in a structured way, sometimes enabling richer search results.
Project and contract terms
Discovery: The early phase where goals, users and requirements are explored before design and build.
Scope: The agreed list of what will be delivered.
Scope creep: Gradual growth of a project beyond the original scope, usually adding time and cost.
MVP (Minimum Viable Product): The simplest version that delivers core value, launched to learn before investing more.
Agile: A way of working in short cycles, delivering pieces regularly and adjusting based on feedback.
Sprint: A fixed period, often one or two weeks, in an agile project.
Waterfall: A sequential way of working where each phase finishes before the next starts.
Fixed price vs time and materials: Two common pricing models. Fixed price agrees a total for a defined scope. Time and materials bills for actual hours.
Technical debt: Shortcuts in code that save time now but make future changes harder and more expensive.
SLA (Service Level Agreement): A contract setting response times and service standards for support or hosting.
Handover: Transferring code, accounts, credentials and documentation from the developer to the client.
Questions worth asking
With these terms in hand, you can ask practical questions:
- Who owns the domain, hosting account and code repository?
- Is there a staging site, and how are changes deployed?
- How often are backups taken, and where are they stored?
- What is included in maintenance, and what is billed separately?
- How will the site perform on Core Web Vitals and mobile speed?
Next step
Bookmark this page and keep it handy when you review your next proposal or project update.
If you are planning a website or web application and want a team that explains things in plain language, see our Turn visitors into customers services.
