HTTP (Hypertext Transfer Protocol) is the set of rules for transferring files between clients and servers on the World Wide Web. Communication occurs through HTTP requests from clients to servers and HTTP responses from servers to clients. A typical request/response cycle involves a browser requesting an HTML page from a server, which returns the page, and then the browser requesting and receiving additional files like stylesheets, images, and JavaScript code referenced in the HTML. An example is provided of an HTTP request from a browser to a server for a youtube.html page and the corresponding response.