git init turns an ordinary folder into a Git repository. It does one concrete thing: creates a hidden .git/ directory next to your files.
Think of .git/ as Git's notebook. It records every snapshot you take, every branch you create, every config you set. Your actual files stay where they are — Git just starts watching them.
Run it inside any directory and that directory becomes trackable. Delete .git/ and you're back to a plain folder. Nothing else moves.