Hi, These are [[Profiles - Where Firefox stores your bookmarks, passwords and other user data | Firefox profiles]]. You can go to ''about:profiles'' and open the profiles whose names correspond to the folder names to see what's in there (to open a profile, just click '''Launch profile in new browser''' under it). There should be one you use daily (it will have "This is the profile in use and it cannot be deleted" above it), which you probably don't want to delete. Regarding the others, it's up to you and depends on the data they contain.