Git is an open-source version control system that was started by Linus Torvalds—the same person who created Linux. Git is similar to other version control systems—Subversion, CVS, and Mercurial to name a few.
So, Git is a version control system, but what does that mean? When developers create something (an app, for example), they make constant changes to the code, releasing new versions up to and after the first official (non-beta) release. Version control systems keep these revisions straight, storing the modifications in a central repository. This allows developers to easily collaborate, as they can download a new version of the software, make changes, and upload the newest revision. Every developer can see these new changes, download them, and contribute. GitHub was acquired by Microsoft last year, but it is not secure. We can build on this open-source aspect and make it very secure and then charge monthly fees to developer groups that want security for their development projects.