In reply to Miroslav Glavic.

You can run Git on your own servers. This requires setting up your own server and installing Git and whatever else you need/want and requiring you to manage the full technology stack. Github, GitLab and Bitbucket do all that for you and host it on their own servers and provide other additional features that many developers find useful.

As for the big deal with Git - its a very efficient, distributed version control system with excellent support which is why its very popular with developers. See https://git-scm.com/ for more info on Git.

Anyway back to your original question - you can install and run Git on your own. Or you can use one of those mentioned Git services.