Question about Musescore file format

Hello everybody.
I am not exactly new to MS, I´ve been using it for a good couple of years to transcribe my piano music. But I just got a new computer and downloaded the last version, and now I find that there seems to be two files for every piece. One with the piece´s name ending with .mscz, and the other with just the name but accompanied by a little blue squiggly logo. So when I open a score to work on it, which one should I open? And furthermore, if I move a score from one folder to another, should I move both versions? Are changes in one reflected in the other? It seems mighty confusing to have to deal with two separate files for each piece but I guess there must be some reason behind it.