Hg Pull vs. Update to branch tip

Command line hg tells this:

$ hg help pull

...

Pull changes from a remote repository to a local one.

...

-R is specified). By default, this does not update the copy of the
project in the working directory.

vs.

$ hg help up

...

Update the repository's working directory to the specified revision, or the tip of the current branch if none is specified.