Shimano Groupset Hierarchy

A bicycle groupset consist of the mechanical components installed on the bicycles frame. The groupset includes: the crankset (which includes the chain rings and the crank arms), the bottom bracket (the bearings through which the crank arms rotate), the brake levers and shift levers, which are usually combined into one lever (commonly referred as the brifters, or in the case of Shimano, STI levers), the rear derailleur, the front derailleur (not present on one-by drive trains), the cassette (which contains the gear sprockets, also known as cogs), the chain, and the brakes.