An airplane relies on thrust from its engines. There are many possible kite shapes.
Wind moving across the sail of a kite creates pressure.
Lift results from this wind pressure being deflected along the face of the kite. In other words, the wind pushes up on the kite. Think of wind pressure like a hand, pushing the kite up into the sky and holding it there. If the hand is removed, the kite will fall. At the same time, wind passing over the top of the kite creates an area of low pressure, like a vacuum, along the back of the kite.