For the active part (top) to gain pleasure, dominating the passive counterpart (bottom) takes centre stage.
Most passives are concerned with relinquishing all responsibility. However, SM does not always have to involve sexual acts. Verbal humiliation or "just" the use of whips, canes and restraints can also provide sexual satisfaction.
Trust is the top priority in BDSM. That's why you shouldn't tie yourself directly to a St Andrew's cross at an S&M sex party and let strangers whip you. If S&M toys are used, they should be thoroughly disinfected for each new partner to avoid possible infections.
ICH WEISS WAS ICH TU is the gay prevention campaign of Deutsche Aidshilfe.