HTTP is both familiar and mysterious. Whenever we browse the Web we take it for granted that if we enter a URL, we will get a web page in response. This request by the browser is answered with a response by the server.
Underneath the covers HTTP does its thing (and does it billions of times a day): it opens a communication channel between two computers, negotiates what to send and how to send it, and reports its success or failure before closing down and moving on to its the next request.