Puissance is a show jumping competition where horse and rider attempt to clear a very high solid wall, often over 7 feet high. The solidity of the wall makes it psychologically intimidating, as the horse cannot see what lies on the other side. Like all jumps in show jumping, the wall is not really solid - it is made of stacked blocks that will fall away at a light touch. This means a light touch might knock the top off, making you lose, but it also helps prevent injury should the horse and rider misjudge the jump. Nonetheless, a bad landing can cause serious injury to horse or rider.
All horses and ponies can jump a few feet (an important skill when escaping predators in the wild), but only a few are physically and mentally capable of being trained to jump at a competitive level.