Noun
That part of a bridle or halter which encompasses the head.
Source: Webster's dictionaryHalters main A halter (US) or headcollar (UK) (occasionally headstall) consists of a noseband and headstall that buckles around the horse's head and allows the horse to be led or tied. Source: Internet
Bits main A pelham bit with a jointed mouthpiece A bit is a device placed in a horse's mouth, kept on a horse's head by means of a headstall. Source: Internet