Git is a version control software. If your not a programmer, it might be useless to you.
It simply store each version of your code (files) in a repository (a directory, a local database or a distant database). And after you can go back in the version. If the programmer brakes something, it’s easier to compare and find the differences.
Atlasssian has a very detailed Git Tutorial.Ok, they sell a private repository application. So if their clients are more knowledgeable, they have less questions. A good business model from my point of view.
Here’s a 10000 ft view of the concept that helps me understand the application and commands.