The two most common types used in kitesurfing are the waist harness and the seat harness.
A waist harness sits around the waist and is the most common option among independent riders. It gives the hips and legs more freedom, allows a greater range of movement and works well for most riding styles, including freeride, jumping, freestyle and wave riding.
Fit is especially important with this type of harness. If it is too large, poorly matched to your body shape or not tightened correctly, it can ride upward under load. Beginners notice this more often because they tend to keep the kite high and spend more time in the water.
A seat harness is secured around both the waist and the legs, so it is much less likely to move upward toward the ribs. The hook normally sits lower, which can also make kite control easier during the first stages of learning. This is one reason seat harnesses are commonly used in schools. They can work very well for beginners, children, and riders whose body shape makes waist harnesses ride up constantly.
The downside is that a seat harness fixes the hips more firmly and provides less freedom of movement. For that reason, many riders switch to a waist harness once they become more confident.
That does not mean a waist harness is automatically “better” or that a seat harness is only for beginners. They are simply different designs, and the best choice is the one that gives you the best control and comfort.