Briefly outline how a skydiver reaches terminal velocity.

This question is relating to the balancing of forces on a moving object.
The force on the skydiver will be equal to its weight multiplied by its acceleration (the acceleration will be equal to 9.8m/s/s - acceleration due to gravity). As they accelerate, there is a drag force due to air resistance which increases and the divers speed increases. The resultant of these two forces is the thing that allows the skydiver to continue to accelerate. The drag force will increase until it is equal to the force from the weight of the skydiver. When these two forces are equal, they will cancel out and there will be no acceleration i.e. the skydiver is moving at constant speed - terminal velocity.