A halter, or headcollar, is headgear that is used to guide an animal; it fits over the back of the neck and across or around the animal's muzzle so that, when a handler pulls on the muzzle end of the halter, the animal's head turns towards the handler.
Halters are commonly used on horses and sometimes on cattle, dogs, and other animals.
The primary difference between a halter and a bridle is that the latter has a bit that goes into a horse's mouth, providing even greater control.