@theycallmemo
Who's on mech?

@theycallmemo for cyclists its the rear derailleur that moves the chain across about 5-12(!) different gear sprockets. If you are not intending to try and win a race, or you have an #e-bike 7-8 are sufficient and less hassle to deal with (like when your front levers go out of index and the chain slips between gears and it all needs adjusting again).