Masochism is the counterpart to sadism, the sexual pleasure or gratification of having pain or suffering inflicted upon the self, often consisting of sexual fantasies or urges for being beaten, humiliated, bound, tortured, or otherwise made to suffer, either as an enhancement to or a substitute for sexual pleasure. The name is derived from the name of the 19th century author Leopold von Sacher-Masoch, known for his novel Venus in Furs that dealt with highly masochistic themes.
A masochist does not in general take pleasure in any arbitary form of pain, only in pain received under the pretext of enforcing authority, and typically only that of a sexual nature. Likewise, a sadist usually only takes pleasure in pain that is inflicted for reasons of punishment and control, and most often for the indirect pleasure of the masochist. Many sadomasochistic activities involve only mild pain or discomfort. Often they are focused primarily on roleplay.
The term BDSM has been created to describe the quite common activities between consenting adults that contain sadistic and masochistic elements. Many behaviours such as erotic spanking and love-bites that many people think of only as "rough" sex also contain elements of sado-masochism.
A Jungian View
"Masochism is an art of holding oneself in oppositional extremity. The masochist sees himself living – appears to live – in extremis, at the very edge of danger, madness, death. A masochist's pleasure is extremely painful and his pain, extremely pleasurable. Often opposite feelings like pride and humiliation are present simultaneously, both torturous, both pleasurable. In the midst of such emotional extremity, the need and feeding of the masochistic compulsion is clearly, itself, part of the torture and pleasure. There is pride in this cliff-hanging extremity, in maintaining these impossible oppositions without plunging over the edge. It is an extreme pride, a pride of extremity, of going to extremes and surviving. It is a pride of promethean proportions."
- by Lyn Cowan - Masochism: A Jungian View (page 92) ISBN 0882143670
See the article on sadomasochism for more information and links on this topic.