The nickname of James Potter when transformed into his animagus as a stag. Prongs was in a jokester group known as the Marauders with Remus Lupin (Moony), Sirius Black (Padfoot) and the traitor, Peter Pettigrew (Wormtail).
James Potter suffered a tragic death protecting Lily and Harry Potter from the evil Lord Voldemort.
During his time at Hogwarts, it was commonly acknowledged the Prongs was a Chaser of Gryffindor, a ladies man (but not nearly as handsome as Sirius), and the main taunter of Severus Snape.
James fought in the first Wizarding War as a member of the Order of the Phoenix with his friends.
He was betrayed by Peter Pettigrew, but Sirius was blamed.
Harry's patronus is a stag--- Harry once believed this patronus was actually the re-incarnation of his father. Sad, but untrue.