Git is a tool that keeps a record of changes to files in a project. It is like a notebook that saves named snapshots, so you can see what changed or return to an earlier version.
For example, if an AI coding tool changes several files and the page stops working, Git can help you compare the new files with an earlier snapshot. You can also save a useful change before trying something risky.
Git records changes on your computer unless you share them with an online service. Saving a change in Git does not automatically publish your website or send the files to someone else.