I was also confused by this, and below is what I have learned.
When you clone a repository, for example from GitHub:
origin
is the alias for the URL from which you cloned the repository. Note that you can change this alias.
There is one master
branch in the remote repository (aliased by origin
). There is also another master
branch created locally.
Further information can be found from this SO question: Git branching: master vs. origin/master vs. remotes/origin/master