Caster, a.k.a. “castor”, is the difference between the angle of the steering block pin (aka “kingpin”) and vertical (90 degrees from the main part of the chassis) when viewed from the side of the car.
On most cars, caster is calculated by adding the kick-up angle of the chassis and any additional caster added by the hub carrier (aka “caster block.”)
Kick-up is also known as “rake.” The kick-up angle is the upward angle of the front of the chassis (0 degrees kick-up would be flat.)
More kickup / caster
Less kick-up / caster