Git is a "version control system". It is used by programmers to keep track of the successive changes in their code (all the versions are stored in a "repository" with a version number). Git also provides a team of programmers with various tools which help them solve problems related to concurrent modifications of the code.
Git is thus a professional way to share code between developers.
If you work on windows, git is not provided by Microsoft with the OS. You must install it before the next steps.
