What is backend?

Question

In the introduction to html the php is reffered to as a backend.. I wanted to know what is the meaning of backend.

Answer 1

It simply means that PHP codes are executed in the background without the user being able to see what's being executed. If you upload a new picture in a webpage then the HTML code of that page submits your uploaded code to the back-end codes which handles your uploaded file. Understand backend as the things that happen in the background.