A-Spec is where you race the car yourself. B-Spec is where a computer car races for you, but is usually slower than if you drive the car in A-Spec. However, B-Spec can be good for endurance races because you can speed the race up to 3x as fast.
Both are racing, one just driven by the computer and you control the pace, when to pass, and when to pit (although the game does automatically in B-Spec).
A-Spec is like a normal racing game - you drive
B-Spec is like a manager game (such as a football manager one) - you aren't driving, the computer is, but you can make decisions as to how the computer performs.
