HTTP is the protocol used to deliver web pages over the internet. It uses a request/response model where clients make HTTP requests to servers, which respond with HTTP responses. Common HTTP request methods include GET, POST, PUT, DELETE, and HEAD. A request contains an initial line specifying the method, URL, and protocol version. A response contains a status line with the protocol version, status code, and description. Common status codes include 2xx for success, 3xx for redirects, 4xx for client errors, and 5xx for server errors.