On GitHub, saved changes are called commits.
Understanding the GitHub Flow
When you're working on a project, you're going to have a bunch of different features or ideas in progress at any given time – some of which are ready to go, and others which are not.
Branching exists to help you manage this workflow.
When you create a branch in your project, you're creating an environment where you can try out new ideas.
Changes you make on a branch don't affect the master branch, so you're free to experiment and commit changes, safe in the knowledge that your branch won't be merged until it's ready to be reviewed by someone you're collaborating with.
ProTip
Branching is a core concept in Git, and the entire GitHub Flow is based upon it. There's only one rule: anything in the master branch is always deployable.
Because of this, it's extremely important that your new branch is created off of master when working on a feature or a fix. Your branch name should be descriptive (e.g., refactor-authentication, user-content-cache-key, make-retina-avatars), so that others can see what is being worked on.
Commits also create a transparent history of your work that others can follow to understand what you've done and why.
ProTip
Commit messages are important, especially since Git tracks your changes and then displays them as commits once they're pushed to the server.
Again：官方的是最好的，永远要看第一手资料