GitHub
An online place to store code, track changes, and work with others using history you can always roll back.
Think of a shared filing cabinet with a time machine. GitHub hosts your project so you can save versions, compare changes, and restore old copies.
It matters because features change, mistakes happen, and more than one person or tool might edit files. GitHub is built on Git, a change tracker that records snapshots called commits, and lets you create branches, parallel lines of work you can later merge.
In practice your app lives in a repository, a tracked project folder. You commit changes with messages, open pull requests to review changes, and keep migration files and other history in one place.