Caster is a bit tough to define. If you’re viewing the side of a vehicle, the caster angle identifies the forward or backward slope of a line drawn through the upper and lower steering pivot points. Think of a motorcycle and its front steering forks and front tire. Its angle is towards the rear of the motorcycle, so it has positive caster. Negative is just the opposite. Long story short, positive caster helps your vehicle go straight, much like the motorcycle.
Camber is the angle of the wheel, in degrees, when viewed from the front of the vehicle. Positive camber is when the top of the wheel is leaning out from the center of the car. Negative camber is when the top of the wheel is leaning into the car. If the wheel leans too far from the center, uneven wear will occur. (However, negative camber helps racing cars improve cornering.)
Toe is the difference in the distance between the front of the tires and the back of the tires. Usually, tires are set so that they are parallel with each other. If the fronts of the tires are closer, the wheels are toe-in. If the rears of the tires are closer, the wheels are toe-out.