Glossary

The web, in plain English.

The technical words people throw at you without always explaining them. Here are the main ones, in plain terms, so you can follow a conversation about your site without feeling lost.

A
Accessibility (RGAA / WCAG)
Making a site usable by everyone, including people with low vision, blindness, or reduced mobility. The RGAA (France) and WCAG (international) are the good-practice frameworks. It's also a legal obligation for many businesses since 2025.
API
A "socket" that lets two pieces of software talk to each other. When your site shows a Google map or customer reviews, it goes through an API.
C
Cache
A temporary memory that keeps a ready version of your page to serve it faster, instead of rebuilding it on every visit. One of the biggest speed levers.
Canonical (canonical tag)
A label that tells Google "the official version of this page is this one". It prevents slightly different addresses from being seen as duplicate content.
CMS
"Content Management System". Software for managing your site's content without coding (WordPress, Shopify, PrestaShop...). It provides an admin interface.
Core Web Vitals
Three Google measurements of the real experience: display speed (LCP), visual stability (CLS) and responsiveness (INP). They influence your ranking.
D
DNS
The internet's directory. It translates your domain name (example.com) into a server address. It's also where emails are configured (SPF, DKIM, DMARC).
Domain name
Your site's address (example.com). You rent it yearly from a registrar. It's separate from hosting, which stores the site.
F
Framework
A toolbox for developers that speeds up building a bespoke site (Next.js, Laravel, Spring Boot...). More flexible than a CMS, but without an admin interface out of the box.
H
Hosting
The server that stores your site and keeps it available 24/7. Its quality sets the performance ceiling: an overloaded host slows everything down.
hreflang
A tag that tells Google the language versions of a page (FR, EN...). Essential on a multilingual site so Google doesn't treat the versions as duplicate content.
HTTPS / SSL
The padlock in the address bar. It encrypts the exchanges between the visitor and your site. Essential: without it, browsers show a warning and Google penalises you.
L
Lazy loading
Images only load when you scroll to them, instead of loading everything at once. The page displays faster.
M
Meta description
The short text that appears under your page's title in Google. It doesn't directly affect ranking, but a good description makes people want to click. Generate yours.
O
Open Graph (OG)
The tags that decide the preview when you share your link on Facebook, LinkedIn or X: title, description, image. Without them, the share looks dull. Check yours.
R
Responsive
A site that automatically adapts to every screen size, from mobile to a large monitor. Non-negotiable today: most traffic is mobile.
robots.txt
A file that guides search-engine robots: which parts to crawl, which to ignore. Badly set up, it lets Google index thousands of useless pages. Generate yours.
S
Schema.org / JSON-LD
A language to describe your content so Google understands it precisely (a product, an article, a business). It enables rich results (stars, prices, FAQ). Generate yours.
SEO (search engine optimisation)
The set of techniques to appear higher in search results without paying for ads. It covers the content, the technical side and the site's popularity.
Sitemap
A map of your site in XML format, listing your important pages to help Google find them. To be declared in Search Console.
SSR / SSG
Two ways to build a page: SSG prepares it in advance (very fast, ideal for stable content), SSR generates it on each request (useful when content changes constantly).
T
TTFB
"Time To First Byte": the time the server takes to start responding. A high TTFB often betrays a host that's too slow. Aim for under 500 ms.
W
WebP / AVIF
Modern image formats, 30 to 70% lighter than JPEG at equal quality. Adopting them noticeably speeds up image-heavy pages.