Git
Git is used to maintain source code. When working with -for example- robot programs in plain text this is an ideal method of keeping track of changes. Next to that, using Git enables working together on the same project/files/documentation.
NOTE: Git is not suitable for binary files.
Read up on installation and configuration:
After installing Git for windows, open Powershell or another console and setup your credentials.
git config --global user.name "John Doe"
git config --global user.email johndoe@example.com