Crankset Summary
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 one or more chainrings attached to the crankarms, which attach the pedals to the crank. 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.

Over the years, many different strategies have propelled crankset development, not the least of which have been the addition of new bottom bracket technologies, the desire for an increased amount of mechanical advantage, and weight savings.

When evaluating cranksets be mindful of weight differences, construction differences (better cranksets are stiffer, and have less play in them), and gearing differences.
Full Article