Make a formatting box similar to Stack Overflow for web application

How to make a text formatting box similar to Stack Overflow. I have following questions which I have no idea.

1. What is it called actually, the technical name?


2. How the text end up at the back end? I mean if I had finished writing the text and formatting with bullets, bold, underline, how does this all formatting information picked and stored at the backend?


3. Some ready-made format boxes avaiable (similar to what bootstrap is for css, readymade components, etc.)