Most beginners start with a seat harness. Seat harnesses are in general more comfortable to wear. It is easier to resist the power of the kite and your center of gravity is positioned lower. A seat harness will have straps to go around your legs so that the harness is like a seat that you wear.
More advanced riders prefer waist harnesses. They allow better control while jumping.
A combination harness is in general a waist harness with a seat part that can be detached. The seat part is normally attached with hook and loop (velcro) to the harness.
Make sure to choose the right size of harness. There are harnesses for children, women and men.
The chicken loop attaches the bar that you use to control the kite to the harness. On the harness is a hook to keep the chicken loop connected. The hook is attached to a spreader bar. It is a metal bar that distributes the power evenly over the harness.