Just to clarify somebody's definitions earlier because they weren't entirely accurate. The Psychological terms and definitions for the following are
Sexual Masochist: A person who gets sexual pleasure/gratification from having pain inflicted onto him/herself.
Ex. Wanting to be a submissive slave girl and getting whipped and chained brutally during sex
Sexual Sadist: A person who gets sexual pleasure from inflicting pain onto another.
Ex. Quite a few many cases of serial killers who abused and injured their victims before killing them out of pleasure.
Sadists I consider are far more dangerous -_-