Allow me to explain, since I have the most book knowledge:
In TKD, they chamber the kicks, and the striking element is the ball or edge of the foot.
Any experienced martial artist will likely have fast kicks-keep that in mind. Some styles lend themselves to seem quicker because of the placement of the kicking leg. For example, most karateka kick with the rear leg which has a further distance to travel whereas the front leg is already closer.