Sadism is defined as social or sexual gratification or pleasure by inflicted pain by other person. The word "sadism" is derived from a french philosopher-writer of sadistic novels Marquis de Sade. The counterpart of Sadism is the Masochism. The sexual gratification or pleasure by reception of pain from being humilliated and tortured is defined as Masochism. The word "Masochism" come from the autor of the masochistic novel Venus in Furs Leopold von Sacher-Masoch.
Commonly interrelated (one person obtain sadistic pleasure by another who obtains masochistic pleasure) are well-knowed as S&M or Sadomasochism.
Now sadism and mosochism are commonly used to describe people's personalities rather than being used for sexual terms. Althought their original meanings the use of these words is not entirely inaccurate. They can be used to point the desire to be controled or to control another person in emotional terms speaking.
Love, sex, violence and pain experiences are strictly associated with the release of several hormones on the human body since humans show many responses while watch, image and hear such experiences.
BDSM is composed by many subdivisions of the alternative culture. Bondage and Discipline (B&D), domination and submission (D&S) and Sadism and Masochism (S&M). While saists enjoy inflicting pain masochist enjoy receiving pain wich, by the way, could be sexual or not sexual. At deeper level, dominance and submission is more internal distinction, not all sadists are dominant neither all dominant are sadists while not all masochists are submissive and not all submissives enjoy pain.