Oversteer

Oversteer occurs during a turn when the REAR wheels of a car do not track behind the front wheels but instead slide (drift) toward the outside of the turn in a more straight-line trajectory. Drifting is the art of controlled oversteer. To drift is to maintain a car in an oversteered position using countersteering, e-brake, throttle and drivetrain inputs.
Since oversteering is encouraged in drifting, worn or used tires are shifted to the back wheels since they offer less traction while tires made with softer compounds that offer more grip are used in front to promote better handling.

Understeer

Understeer is the opposite of Oversteer. Understeer is a loss of traction in a vehicle’s FRONT tires, caused by excessive speed in relation to cornering angle.

Drift Angle

Drift angle is the degree of oversteer a car maintains during a drift. Drift angle is important in competition and is often judged as part of a driver’s style - the more extreme the drift angle, the better.