What your developer said, in English.
42 terms you will hear on sales calls, in proposals and in contracts — each with a plain definition and the line other glossaries leave out: what it means for your money and your risk.
Glossary
Platforms and the build
The words developers use to describe what your site is made of — and what each one costs you later.
CMS (Content Management System)
The software you log into to edit pages, posts and products without touching code. WordPress is the best-known example.
Why it matters: Who can operate the CMS decides your running costs: a familiar system means ten minutes of training for staff; an exotic one means calling the developer for every comma.
Theme / template
A pre-built design system your site wears. Multiple pages usually derive from a handful of templates.
Why it matters: Ten pages from three templates is a fraction of the cost of ten bespoke designs — usually the better deal. Ask any quote how many unique templates it includes.
Plugin
An add-on that gives a platform extra features — forms, SEO tools, checkout add-ons, and so on.
Why it matters: Every plugin is a dependency: it must be updated forever and each one is a possible security hole. More plugins, more maintenance. Unused plugins should be deleted, not deactivated.
Custom post type
In WordPress, a purpose-built content bucket — "case studies", "properties", "team members" — with its own fields and layout.
Why it matters: The difference between a site your staff can maintain and one where every new listing is a developer call. Cheap to plan in, expensive to retrofit.
Headless CMS
A content system that stores your content and serves it to any front end via an API, decoupling editing from presentation.
Why it matters: More flexibility and speed for the right project — and a second system to run forever. Pay for it when the front end genuinely needs it, not for architecture fashion.
Staging environment
A private copy of your site where changes are made and tested before going live.
Why it matters: If a developer cannot show you a staging site, you are the QA department. Insist on one and keep it after launch.
Repository (Git)
The versioned record of your site's code — who changed what, when, with the ability to roll back.
Why it matters: Repo access from day one is the single strongest predictor of a clean exit. A developer who resists it is telling you how the relationship ends.
Deployment
The act of pushing code changes from the repository to the live site.
Why it matters: A documented, repeatable deploy process means changes are boring. Improvised deploys means launch nights are exciting — and not in a good way.
Handover
The documented transfer of everything: credentials, architecture notes, how-to-run-it instructions.
Why it matters: A website nobody else can operate is not delivered. Make the handover pack a contractual deliverable, not a favour.
Glossary
Money and scope
The contract vocabulary. Every one of these words is a place budgets leak.
Scope
The written list of what the project includes — pages, features, integrations, and just as importantly, what it does not.
Why it matters: Undocumented scope is the number one cause of blown budgets. If it is not written down, it does not exist, no matter what was said on a call.
Scope creep
The quiet accumulation of "small" additions after the scope is agreed.
Why it matters: Creep is not free — it is billed somewhere: in change orders, in resentment, or in corners cut later. The fix is a written change mechanism, priced before work.
Change order
A written, priced approval for work outside the agreed scope, signed before that work starts.
Why it matters: Change orders feel bureaucratic until the alternative arrives: a final invoice full of surprises. Good developers volunteer them.
Milestone
A defined checkpoint where specific deliverables are verified and a payment is due.
Why it matters: Milestones make progress verifiable and give you a clean exit ramp: part ways at any gate, pay for what is verified, keep what is built.
Deposit
An upfront payment before work begins, typically 10–50% of the project.
Why it matters: Deposits are normal; full payment upfront is not. Anything above 50% before delivery should make you ask hard questions.
Fixed price vs time & materials
Fixed price pins the total to a written scope; time & materials bills actual hours, flexing as the work evolves.
Why it matters: Fixed price shifts risk to the developer (so the scope must be airtight); T&M shifts it to you (so the reporting must be honest). Neither is wrong — ambiguity between them is.
Discovery phase
A short, paid engagement to turn "we need a website" into a written, quotable specification.
Why it matters: On fuzzy projects, paying for discovery is how you get comparable quotes instead of guesses. It is not padding; it is the quote being manufactured.
Retainer
A recurring monthly fee for ongoing work — maintenance, updates, small improvements.
Why it matters: Most market retainers sit between $500 and $3,000/month. A retainer quote that cannot say what it covers, its response times, and how it cancels is a subscription, not a service.
Glossary
Speed and search
The metrics Google actually measures — and the words agencies use to sound like they do.
Core Web Vitals
Google's three user-experience metrics: loading (LCP), interactivity (INP), and visual stability (CLS).
Why it matters: They are a ranking input and a conversion input — slow sites bleed both. A good developer quotes targets ("LCP under 2.5s") instead of saying "we optimise".
LCP (Largest Contentful Paint)
How long the main content of a page takes to appear. Target: under 2.5 seconds.
Why it matters: The single number most correlated with visitors staying. Ask any proposal what LCP it commits to, on mobile, on a normal connection.
CLS (Cumulative Layout Shift)
How much the page jumps around while loading — the banner that slides down as you tap a button.
Why it matters: Layout shift directly causes mis-clicks and lost form submissions. It is usually an image-sizing discipline, cheap at build time, annoying later.
CDN (Content Delivery Network)
A global network of servers that serves your site's files from near the visitor instead of one distant data center.
Why it matters: A CDN is often the cheapest meaningful speed upgrade available — sometimes free. A proposal without one for an international audience has a hole.
Caching
Storing ready-made copies of pages and assets so they do not get rebuilt for every visitor.
Why it matters: Caching done well is invisible speed. Caching done badly is the reason your client "still sees the old site" — it needs a documented purge process.
Meta tags
The page title and description shown in search results and social shares.
Why it matters: They are your ad copy in the search results. Unique per page is table stakes; a generator that spits out duplicates is a quiet traffic leak.
Structured data (schema)
Machine-readable labels on pages that tell search engines what things are — a service, a price, an FAQ, a business.
Why it matters: This is how pages earn rich results instead of plain blue links. Cheap to include at build; routinely forgotten.
Sitemap.xml
A file listing every URL you want search engines to know about.
Why it matters: Should be auto-generated and submitted at launch. Its absence on a new site is a two-week ranking delay for no reason.
Robots.txt
A file telling crawlers which areas of the site they may fetch.
Why it matters: A misconfigured robots.txt can quietly deindex an entire site. It is five lines long and worth reading once.
Canonical URL
The tag that declares which URL is the official version of a page when several variants exist.
Why it matters: Without it, www vs non-www and parameter URLs split your ranking signals across duplicates — a slow, invisible leak.
301 redirect
A permanent signpost that a URL has moved, passing visitors and search equity to the new address.
Why it matters: Redirects are the whole ballgame in migrations. Every old URL needs a mapped destination, or the rankings die at the 404s.
Alt text
The written description of an image, read by screen readers and shown when images fail.
Why it matters: Accessibility obligation first, cheap SEO second. Missing alt text fails real users and audits alike.
Glossary
Security and operations
The boring words that decide whether the site survives contact with the internet.
SSL / TLS certificate
The certificate that makes your site load over HTTPS and encrypts traffic.
Why it matters: Non-negotiable: browsers flag HTTP sites as unsafe, and forms without encryption are a liability. It is free (Let's Encrypt); nobody should charge you monthly for it.
Backup
A restorable copy of the site's files and database, stored away from the server.
Why it matters: A backup on the same server is a coincidence, not a plan. Ask where backups live, how old the newest is, and — the killer question — when a restore was last tested.
Tested restore
Actually rebuilding the site from a backup, on a staging environment, proving it works.
Why it matters: An untested backup is a hope. Restore drills are the difference between a bad hour and a dead business.
Uptime monitoring
An external service that checks the site is up and alerts a human when it is not.
Why it matters: Customers find out about outages before owners do, otherwise. Monitoring is a few dollars a month and non-optional for a revenue site.
Two-factor authentication (2FA)
A second proof of identity beyond the password — a code, an app, a key.
Why it matters: Passwords leak constantly. 2FA on hosting, CMS admin and domain registrar stops the majority of account-takeover site defacements.
Access credentials
The logins that control everything: domain registrar, hosting, CMS admin, email, analytics.
Why it matters: All of them should be in your name from day one, held by you, lent to the developer. The reverse arrangement is how businesses lose their own websites.
DNS
The internet's address book that points your domain to your hosting and email.
Why it matters: DNS is where "we lost the domain" stories start. Know your registrar, keep the account in your name, and lock transfers.
Maintenance plan
The recurring arrangement for updates, backups, monitoring and small fixes after launch.
Why it matters: A site is a subscription with occasional capital expenses, not a purchase. The plan should state what it covers, response times, and how it cancels — in writing, before launch.
Glossary
Ecommerce
Store vocabulary — where every term has a fees-and-failure story attached.
Payment gateway
The service that actually processes card payments at checkout — the processor, not the cart.
Why it matters: Gateway fees (typically ~2–3% plus a fixed amount) are a permanent tax on revenue. Which gateway, at what fees, with what alternatives, is a launch decision, not a detail.
Checkout flow
The steps between "buy" and "paid": cart, address, shipping, payment, confirmation.
Why it matters: Most cart abandonment happens here. Every extra field and surprise cost is a measurable leak — test it yourself, with a real card, before launch.
Abandoned cart email
The automatic follow-up sent to shoppers who left at checkout.
Why it matters: One of the highest-ROI emails in ecommerce and cheap to set up — if it is scoped into the build instead of discovered missing after the first Christmas.
Tax and shipping zones
Rules that decide what each customer is charged based on where they live.
Why it matters: Boring, fiddly, and legally load-bearing. This is the line item where store builds quietly overrun — it belongs in the quote, tested with real scenarios.
Product data migration
Moving the catalog — products, variants, images, descriptions, categories — to the new platform.
Why it matters: Frequently the single largest hidden cost in a store project. Get an explicit answer: who exports, who cleans, who enters, priced how.
Quarterly, and only when the numbers move
Get the rate report before you negotiate.
Updated rate bands across the major stacks and regions, plus what changed and why. No other email.