"http" stands for HyperText Transfer Protocol.

"Protocol" is a fancy word for "a method for getting something done." In this case, the "something to get done" is connecting to a server on the Internet. for connecting to a server on the Internet. http is the method used to connect your web browser to a server so that you can access webpages, pictures, videos, etc. from that website.

Web pages are written in a computer language called HTML. http is designed to transfer HTML documents (webpages) from a web server to your computer through your browser.

There are other protocols besides http, but http is the one used to connect to webpages, so it is by far the most common protocol used on the Internet today.

URL's usually begin with "http" because that information tells your web browser how to connect to the server the URL points to. However, you (usually) don't have to type in the "http" at the beginning of a URL. If you don't tell your browser what protocol to use, it is programmed to automatically use http to try to connect to that server.