why are 2 copies saved with different names?

Hi and thanks folks for being here to help. Quick question: I used Windows Explorer to look at the folder that MuseScore created for me, and saw that for each compressed MuseScore file there is also another one that appears to be the same in everything but name, and the name has a leading dot and a trailing comma so it doesn't show up in the Open File dialog in MuseScore. I actually changed the name of one in order to recover a file that I had mistakenly overwritten with the wrong version, and it seems to be okay.

Okay here's the quick part of the question :-) Why does MuseScore do this? What's it really for?