A cam is a rotating component used in a mechanism in order to transform a movement from a circular to a reciprocating motion. A crank performs the opposite action.
A common example of a cam mechanism is that found on a car engine where the camshaft translates the rotary motion of the engine into a reciprocating motion to operate the intake and exhaust valves on the engine cylinders.
Please see the related links for an example animation and more detailed explanation.
function of cam follower
So you can adjust the throw of the cam
"What is the VVT Cam Gear Unit?"
Describe the various hardware equipment used in cad/cam?
cam in an ic engine is made up of HIESPEED STEEL OR THAT CONTAIN HIGH %OF CARBON THAT CONTAIN .2% CARBON