There is quite a bit of physics involved in skydiving, but lets start with the basics. Once you leave the plane there are essentially only two forces acting on you: the Earth's gravity pulling you straight down, and friction with the air. The friction with the air mostly adds up to push in the opposite direction from the direction you are moving, so basically it pushes up on you and your equipment.

Air resistance increases as your speed increases, so when you first start dropping and are moving slowly, gravity is stronger than the air resistance and you speed up, accelerating towards the ground. However the faster you drop, the stronger the air resistance is and so eventually you are moving so fast that the air resistance is equal in strength to gravity and you don't accelerate any more. You have reached terminal velocity for your current body position.
Why does body position come into it? Because air resistance also depends on the shape of the object (you) and so by tucking in your arms and legs you can reach a faster terminal velocity than if your arms and legs are spread out. But skydivers don't splay their arms and legs to slow down per se (if they were afraid of high speeds we can imagine they would have chosen a different sport). They are trying to achieve a position of dynamic stability.
Dynamic stability is what allows an arrow to fly nose first. If the arrow starts to flip sideways, the air resistance against the fletching is greater than the resistance at the nose, and the arrow automatically goes back to its initial orientation. Likewise, skydivers don't want to be tumbling end over end and out of control, so they trail their arms and feet behind them to act like the feathers on the arrow.

I think a picture will be nice.

Tanx man tried doin it ma netwk jst kept pipin up

gravity?

mikeansy: gravity?

Air pressure n gravity