whatever the rider decides to put there.
The threads on bicycle pedals are American Standard.
Motor cars and Bicycle's both have pedals.
bicycle
How fancy do you want them to be? Cheap pedals are die-cast. Expensive pedals are machined.
To do bicycling you need a bicycle. And the bicycle is a man-made item relying heavily on techology to provide all the bits and pieces.
Two
That'd be the crank arm.
Velocipede
A motorcycle has a motor and no pedals
Because metal is durable and leightweight
the amount of force spinning the pedals
Pedals and seats