The bit and the snaffle bit are types of mouthpiece, that is, tools for guiding and managing the horse that are placed inside its mouth and are supported by the headstall (an integral part of the harness that wraps around the horse's head). Both rest, inside the mouth, in the toothless part located between the incisors and premolars (called bars).
The bit is made up of metal rods arranged in an "H" shape, at the ends of which there are rings for attaching the reins and the headstall. It is a very rigid mouthpiece in which the pull of the reins is amplified by the length of the lateral rods.
The snaffle bit is a softer mouthpiece than the bit and is made up of a single metal rod (called cannon) that can be rigid or articulated, and two rings, placed at the ends, on which to attach the reins and the headstall straps.