A physical force equivalent to one unit of gravity that is multiplied during rapid changes of direction or velocity. Drivers experience severe G-forces as they corner, accelerate and brake.
When a car slides, it can cause little bits or rubber ('grains') to break away from the tyre's grooves. These then stick to the tread of the tyre, effectively separating the tyre from the track surface very slightly. For the driver, the effect is like driving on ball bearings. Careful driving can clear the graining within a few laps, but will obviously have an effect on the driver's pace. Driving style, track conditions, car set-up, fuel load and the tyre itself all play a role in graining. In essence, the more the tyre moves about on the track surface (ie slides), the more likely graining is.
A bed of gravel on the outside of corners designed with the aim of bringing cars that fall off the circuit to a halt.
The amount of traction a car has at any given point, affecting how easy it is for the driver to keep control through corners.