Git: "+refs/heads/<branch>:refs/remotes/origin/<branch>"

Jenkins Git plugin generated the below command in console output based on my ref spec

1. What's the difference between below 2 commands? Their output looks little different. I have given their output below:

   Command 1:

   git fetch --no-tags --progress repo.git +refs/heads/qa:refs/remotes/origin/qa --depth=1

   Output:

   From <repo>
    * [new branch]      qa         -> origin/qa
   

   Command 2:

   git fetch --no-tags --progress repo.git refs/heads/qa --depth=1

   Output:

   From <repo>
    * branch            qa         -> FETCH_HEAD
   

2. What does FETCH_HEAD here mean?

3. I believe refs/heads/qa is local working copy of 'qa' branch and refs/remotes/origin/qa is remote 'qa' branch. But, what does this convention imply?

   +refs/heads/qa:refs/remotes/origin/qa