Client Server

Hypertext Transfer Protocol (HTTP) is an application-layer protocol for transmitting hypermedia documents, such as HTML. It was designed for communication between web browsers and web servers, but it can also be used for other purposes

https://developer.mozilla.org/en-US/docs/Web/HTTP

What do I need to know about HTTP?

So you want to develop a web application - what do you need to know about HTTP to be able to do that? Most web applications run on web servers. They field requests from web clients (primarily web browsers), and provide responses (usually web pages). But the good news is that HTTP isn’t as complicated as something like a programming language might be, and what you need to know really revolves around the two basic building blocks mentioned above - requests and responses.