Git is a version control program, which means that its job is to help you take “snapshots” of your files as you work on them. If you’ve ever had to manually make “Save As…” copies of something (e.g. a Word document) with -version-1, -version-2… suffixes, you’ve used “version control” (a ghetto version of it, anyway). Git is just a program to do this sort of thing automatically—to easily make (and keep track of) a bunch of snapshots of the files in a directory over time. That way you can fearlessly try things out when you’re programming, knowing that if it doesn’t work out you can just go back to a previous snapshot.
The one final piece of the Git puzzle is that Git allows you to keep these snapshots in sync across multiple computers. These can be any computers—your laptop might be one, but it you might also use another computer in the cloud (which is a good idea, since it doubles as a back-up). The idea is that you can change your files (i.e. create new snapshots) on whatever computer you happen to have handy at the time, and git helps you keep everything in sync.