Remus Lupin is a former professor of Defense Against the Dark Arts, goes by the name Moony by his best friends (James Potter, Sirius Black, and Peter Pettigrew). He is a werewolf, and he transforms in the Shrieking Shack once a month. The werewolf who bit him was Fenrir Greyback.
In the marauder era, Lupin was romantically involved with his best friend Sirius Black. After Sirius was killed off in Order of the Phoenix, Remus tried to move on. He married Nymphadora Tonks, Sirius's cousin, in the hope that she would have similar traits as him, and as an experiment of his sexuality. Remus often feels down during the last years of his life because of this mistake.
Remus is often described as having amber eyes, and shaggy brown hair. He's covered in scars because of his transformations, and he's really powerful despite how skinny he is. Since nobody will hire a werewolf, he can't afford nice clothes, and they are often worn down and patchy.
Remus Lupin: God of chocolate and... homework.