Important files in Firefox that I either already know about or have found and am assuming:
formhistory.sqlite - assuming this is the data that pops up when you type into input boxes, such as your address.
bookmarks.html - assuming this stores your bookmarks, however, places.sqlite is also related to bookmarks. Not sure on this file.
places.sqlite - This contains your browsing history and bookmarks.
localstore.rdf - This is your toolbar setup, but gets corrupted easily.
logins.json - asssuming this is the file you were asking about.
sessionstore.js - this is the most important file to save/keep/copy. This is the one that has your open tabs so you can "restore session" when you open.
sessionstore.bak - the previous "restoresession" that was from the last time you opened FF before your most recent time.
Note: There is also an "import bookmarks" option, so if you are not coping the entire application data Mozilla folder, it may make more sense to do it this way instead of copying files.
Add-Ons and Plugins cannot be easily transferred without copying the entire folder. I would suggest that these be re-installed for people who do not wish to copy the entire Mozilla Application Data folder.
Last edited by mewgirl; 10-15-2014 at 12:41 AM.