The noseband is around the horse's nose. It is a wider strap than the rest of the straps on a bridle. It is often called a caveson. It is held in place about 10 centimetres above the horse's nostrils by a thinner strap that goes up over the horse's poll, just behind its ears. Its purpose is mainly decorative.
But in the case of a grackle noseband, and a few other types of noseband it is best to look at the Google link bleow: