The crankset is the component of a bicycle drivetrain that converts the reciprocating motion of the rider's legs into rotational motion used to drive the chain, which in turn drives the rear wheel. It consists of a set of chainrings, the crankarms. It is connected to the rider by the pedals, to the bicycle frame by the bottom bracket, and to the rear sprocket, cassette or freewheel via the chain.

A crankarm, also know as crank arm and crank-arm, is the lever arm on a bicycle that attaches to the bottom-bracket spindle at one end and the pedal at the other end. The right crankarm has one or more chainrings — sometimes incorrectly called "gears" — attached to it, usually by means of chainring-mounting arms.

References

John Barnett, Barnett's Manual: Analysis and Procedures for Bicycle Mechanics (5th Edition).