For information about the differences between the upstream and the push-remote, see Branching.
Also see the git-fetch(1) manpage.
This prefix command shows the following suffix commands along with the appropriate infix arguments in a popup buffer.
Fetch from the push-remote of the current branch.
Fetch from the upstream of the current branch.
Fetch from another repository.
Fetch a branch from a remote, both of which are read from the minibuffer.
Fetch from a remote using an explicit refspec, both of which are read from the minibuffer.
Fetch from all remotes.
Fetch all submodules. With a prefix argument fetch all remotes of all submodules.
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