General Terminologi of Bicycle Parts – Drive Train
Derailleur: There are two such mechanisms: a front derailleur and a rear derailleur. The front derailleur moves the chain between the selection of gears on the crankset; the rear derailleur moves the chain between the selection of gears on the rear wheel.
Chain: The loop of links that connects the front gears to the rear gears.
Freewheel: The set of rear gears. Freewheels and freehubs have a confusing overlap of terminology. In a general sense, the freewheel is the set of gears that the chain turns in order to apply drive forces to the rear wheel.
Crankset: The mechanism that is turned by the rider’s feet. It consists of two lever arms called crank-arms, one to three gears called chainrings, and a bearing assembly that the crank arms rotate around called the bottom bracket.
Bottom bracket: The bearing assembly that allows the crankset to rotate in the bottom-bracket shell.