Camber is the wheel angle when the wheels are viewed straight from the front. Camber is mainly  tinkered with to alter grip levels.

Negative camber - the wheels lean inwards. This is the most common setup in F1. Negative camber increases grip levels in corners but gives a disadvantage down the straights. 

Positive camber - the wheels lean outwards. While negative camber is the most used setup, some tracks might reward a car setup with positive or asymmetric camber angles (where both wheels point in the same direction). An example where positive and asymmetric camber is used is in oval racing where one wants to match the angle of the bankings.

Illustration: Matthew Somerfield