*A–Z of essential web development concepts* A - API (Application Programming Interface) B - Backend Development C - CSS (Cascading Style Sheets) D - DOM (Document Object Model) E - Express.js (Web Application Framework) F - Frontend Development G - Git & GitHub H - HTTP/HTTPS (HyperText Transfer Protocol) I - Index.html J - JavaScript K - Keywords in SEO L - Layout (Flexbox & Grid) M - Middleware N - Node.js O - OAuth (Open Authorization) P - Progressive Web Apps (PWA) Q - Query Parameters R - RESTful APIs S - Semantic HTML T - Tokens (Authentication) U - UI/UX Design V - Version Control W - Webpack X - XMLHTTPRequest (XHR) Y - YAML in DevOps (used in CI/CD pipelines) Z - Z-index in CSS These are the core foundation of web development, covering both frontend and backend areas. Mastering them will help you build modern, responsive, and secure web applications.