what is caster

Well im trying to find out what caster is. Search doesn't help. But i have an idea what camber and toe in and toe out is but not caster. Can you help me.

http://stockcarracing.com/tipstricks/p87584_image_large.jpg

http://www.stockcarracing.com/tipstricks/31519/

Cool drawing.

Caster gives your steering the 'self-centering' effect as you drive forward, that is, the wheel wants to straighten up and the car move in a straight line.
It does this, as the drawing shows, places the centre of rotation for the steering forward of the center of drag of the wheel (this is where the tire contacts the road.)
For the same reason, in reverse (going at speed) , caster makes the wheel want to flop all the way to one side.

Also Projects The Inclination Of The Wheel Wether It Is In Or Out, I Think

i think you are referring to "camber"

Yep I Was And Thats Becuase I Certified I Need To Check Back At My Books