Imagine you have phone book and to see the address of George Jones you could type in his name and it would jump to that page. You could say his name was hypertext and this is exactly the way a web page works. Many years ago printers would make notations in margins to describe what the printed document should look like, such as text size and color. This was called mark-up. As so often happens these terms have carried over into today. Hypertext Mark-up Language (HTML) is what describes the text on the web. Hypertext Transfer Protocol (HTTP) is a communications protocol for the transfer of information between computers on the Internet. A protocol is just a set of procedures.
Web sites are stored on specialized computers called file servers. When someone wants to see a web site they type in the URL (http://www.website.com) and their computer at home requests the website (HTML) files from the web file server which that URL points to. The web site is then on their home computer for usage.