here are a few cam basics and how a cam can make more power in your car.
a motor is nothing more than an air pump. the more air that is can move through it, the more power you make.
lift is the distance the valve opens
duration is how long in degrees that the valve stays open.
the longer the duration, the longer the valve stays open, and the more air and fuel enters the cylinder on the intake and the more exhaust gets out. making more power.
think of it this way. take a water valve and open it the entire way and close it as fast as you can while the water runs into a bucket. then take the same valve and open it slowly and close it slowly while the water runs into a bucket. now see how much more water is in the bucket that you opened and closed slowly. the same principle aplies to the duration of your cam. this is just one way a cam makes you more power. also when you have a longer duration, it helps scavage the exhaust out of the cylinder also.
the camshaft is the brains on the mechanical side of the motor.
i hope i explained this ok, and i know someone out there may dispute this, but, i just had to post this
for more info on cams click this link