A git user can identify himself on his local computer using the following commands:
$ git config --global user.name "John Doe" $ git config --global user.email email@example.com
Or, for specific repository:
$ git config user.name "John Doe" $ git config user.email firstname.lastname@example.org
Then every commit is supported by the configured user information.
Hosting services (like GitHub and BitBucket, for example) try to match these data in commits with a particular account: