HTTP or Hypertext Transfer Protocol is the main protocol of the World Wide Web. When you request a web page by typing its address into your web browser, that request is sent using HTTP. The browser is an HTTP client, and the web page server is (unsurprisingly) an HTTP server.
In essence, HTTP defines a set of rules regarding how messages and other data should be formatted and exchanged between servers and browsers.
Why Do I Need To Know About This?
Ajax sends server requests using the HTTP protocol. It's important to recognize the different types of HTTP requests and the responses that the server may return. Ajax applications need to construct HTTP requests to query the server and will base decisions about what to do next on the content of HTTP responses from the server.
What Is (and Isn't) Covered in This Lesson
It would be possible to fill the whole book with information on the HTTP protocol, but here we simply discuss it in terms of its roles in requesting web pages and passing information between them.
In this lesson you'll look at the construction of HTTP requests and responses and see how HTML forms use such requests to transfer data between web pages.