Or not so much Word, but Microsoft’s cloud, aka OneDrive.
Revisions. We keep our files on OneDrive, so we can both edit the file and, theoretically, when the one person opens the document they can see what changes the other has made.
It’s working a lot better than it used to. Microsoft seems to have fixed some bugs. The two users are playing nice in the same file nowadays, which is more than they used to. (Four users really, since there are two at home and two for the daily commute).
Until we start tracking changes.
Well, actually, track changes is fine. The problem is accepting changes.
You accept the changes on one computer. Everything looks fine.
Then you open the file on another computer. Only to find that both sets of changes have disappeared altogether, or the changes have been inserted twice.