What does git push origin HEAD mean?

If you want to push into the specific remote branch you can run:

git push origin HEAD:<name-of-remote-branch>

This is what I encounter when I was trying to push my repo back to the remote branch.

HEAD points to the top of the current branch. git can obtain the branch name from that. So it's the same as:

git push origin CURRENT_BRANCH_NAME

but you don't have to remember/type the current branch name. Also it prevents you from pushing to the wrong remote branch by accident.

If you want to push a different branch than the current one the command will not work.