Mozilla used a mechanism where you had to enter a pairing code shown in one browser into another browser in order to sync up devices. Now they are testing a new version of Firefox Sync where you enter a username and password. You can safely and easily use your bookmarks, opened tabs, and passwords between multiple devices with a simple password sign-in. This can be important for those who use PC’s, tablets, smartphones, etc. Pretty interesting.
Sources:
Paul Dundon 