Fundamentally, Git is a version control system, meaning that it controls the versions of the files under its care.
Most folders can theoretically be made into a Git repository, though it's usually code or configuration that gets this privilege.
When you check out a repository, you get a snapshot of where the code on the branch is at the time you check it out. If you then make changes, those changes need to be staged and either kept in a separate branch or merged into the branch you changed.
In the real world, there are a few different ways that people tend to use Git, and some relatively popular tools and practices that have ...