For information about the differences between the upstream and the push-remote, see Branching.
Also see the git-pull(1) manpage.
This prefix command shows the following suffix commands in a popup buffer.
Pull from the push-remote of the current branch.
Pull from the upstream of the current branch.
Pull from a branch read in the minibuffer.
Instead of using one popup for fetching and another for pulling, you
could also use
magit-pull-and-fetch-popup. See its doc-string for