HTTP, Explained

Every time you open a website, two computers have a short, polite conversation: your browser asks for something, a server hands it back. That conversation is HTTP - the language the web speaks. You've relied on it every day without ever being shown how it works, and that's fine until a page returns 404, a developer mentions a "POST request," or https:// turns red and you wonder if you're about to be robbed.

This guide is the manual nobody handed you. By the end you'll picture exactly what your browser and a server are saying to each other, read a status code without panic, and understand what that little padlock is actually protecting. No deep networking background needed - we start from the conversation and build up.

How to read this

• Want a specific answer right now? Phase 2 has the status-code table - if you just want to know what 404 or 500 means, jump to Phase 2: Methods & Status Codes.
• Want it to finally make sense? Read in order. Each phase builds on the last: the conversation first, then the words it uses, then the details that ride along.

The phases

1. Request & Response - the core model: your browser sends a request, the server sends a response. Plus the anatomy of a URL, the address you're really typing.
2. Methods & Status Codes - the verbs (GET, POST, PUT, DELETE) and the three-digit replies (2xx, 3xx, 4xx, 5xx), with a table and how to read a code calmly.
3. Headers, Cookies & the S in HTTPS - the extra notes each message carries, how sites remember you, and what encryption actually buys you.

This guide stops at the everyday mental model. The deeper machinery - how packets actually travel, ports, DNS, and the layers underneath HTTP - lives in its own guides: How the Internet Works, IP, DNS, and Ports, and The TCP/IP Model. APIs are built directly on top of HTTP, so a future guide on what an API is will link back here.