Ok, so this should be final question and I'll be squared away.
I understand that it transfers the chain drive from the left side of the bike to the right side, but what is the actual use that I would gain from having one? From what I've heard if I don't have one I can still use the pedals on the bike, the pedals wont spin with the motor, and I can still shift gears fine.
I'm still probably missing something, if you can't already tell I'm 100% mechanically illiterate. On that note though, if anyone needs electrical help let me know