Can anyone tell me what a bully stick is

--- I keep seeing it on here as something our babies can chew on but I have never heard of them. My Vet just recommended enzadent -- its an oral care chew. Mattie loves them but 1/2 a stick doesn't last long. Plus it makes his #2 look alittle funny so I don't give it to him very often. These puppy teeth are torcher. Mattie's 11weeks.