Maybe you have noticed that in the previous sections, I used the not very intuitive terms of sender and receiver as they do not represent any specific scenario that you might know but rather all of them in a generic way. The main reason for this choice of terminology is to try to separate HTTP from web applications. You will see at the end of the book that HTTP is used for more than just websites.
If you are reading this book, you already know what a web application is. Alternatively, maybe you know it by other terms, such as website or web page. Let's try to give some definitions.
A web page is a single document with content. It contains links that open other web pages with different content.
A website is the set of web pages that usually live in the same server and are related to each other.
A web application is just a piece of software that runs on a client, which is usually a browser, and communicates with a server. A server is a remote machine that receives requests from...