What is "snuff-movie"

Snuff-Movie is a 2005 gothic horror film by British director Bernard Rose. It stars Jeroen Krabbé as a horror film maker named Boris Arkadin, whose pregnant wife, Mary, was brutally murdered by a Manson-like gang of hippy psychopaths during the 1960s...or was she? An eccentric recluse, Boris makes a come-back when he invites some actors to a large mansion in the English countryside to 'audition' for his new film. But unknown to most of them they are being filmed by hidden cameras linked to a ' snuff' website.