u/Elderon132

Hey guys, I noticed some almost furry, looking residue on one side of the cactus and i'm not exactly sure what it is.Should I be concerned as a mold? I also noticed these scarring lines over it. And i'm wondering what that is about? Just a heads up, i'm a total noob about this, so please explain like you would to a 5 year old lol. Any general care tips are welcome as well. Thanks.