It's a long sword used by the samurai of medieval Japan, it is worn slung under the belt with the edge pointing down and designed to be used on horseback. It's very similar to the katana, however to usual things that distinguish it are, -How it's worn, instead of being held in by the obi(sash) it is slung on it using a loop on the saya(scabbard, sheath), also unlike the katana it is worn with the edge pointing down instead of up. -sometimes the blades are also slightly longer(to reach the enemy from the horse) and made lighter(to be easier to balance in one hand) as well.