You should use source control to back up your files, collaborate with others, and tag your releases.
You can create a local source control repository for a new project or an existing project. Later, when you need to share the project or access it from multiple Macs, you can create a remote repository for it.
If you use Bitbucket, GitHub, or GitLab to manage your remote repository, add the remote repository account in Accounts preferences. If you want to create a new remote repository, create a remote from a local source code repository. If the remote repository exists, clone a project from a remote repository or add an existing remote to your local repository.
After you make changes to your project, view changes in the source editor or compare revisions of a file. Then commit the changes to the source code repository. For remote repositories, pull changes from a remote repository before you commit, and then push the changes after you commit.
In the Source Control navigator, choose a branch in your repository and in the history editor, view the commits. You can filter the commits, view the files in the comparison editor, and email the author of a commit.
You can create a branch in a repository to isolate your changes and not impact others. Later, you merge the two branches in a repository together. You can also tag a commit in a branch to easily check it out later. Especially, tag your commits before you distribute your app. You can also create groups in the Tags folder to organize your releases.