BDSM is a complex acronym derived from the terms bondage and discipline (B&D, B/D, or BD), dominance and submission (D&S, D/S, or DS), sadism and masochism (S&M, S/M, or SM). BDSM includes a wide spectrum of activities and forms of interpersonal relationships. While not always overtly sexual in nature, the activities and relationships within a BDSM context are almost always eroticized by the participants in some fashion. Many of these practices fall outside of commonly held social norms regarding sexuality and human relationships.

Many activities can be found under the umbrella of BDSM, which include—but are not limited to—forms of dominance, submission, discipline, punishment, bondage, sexual roleplaying, sexual fetishism, sadomasochism, and power exchange, as well as the full spectrum of mainstream personal and sexual interactions.

An important distinction is that BDSM is not a form of sexual abuse—although some BDSM activities may appear to be violent or coercive, such activities are conducted with the consent of all partners involved. BDSM relationships and practices are exercised under the philosophy of "safe, sane and consensual" (SSC), or the somewhat more permissive philosophy of "risk-aware consensual kink" (RACK).

Activities and relationships within a BDSM context are characterized by the fact that the participants usually take on complementary, but unequal, roles. Typically, participants who are active—applying the activity or exercising control over others—are known as tops or Dominants. Those participants who are recipients of the activities, or who are controlled by their partners, are typically known as bottoms or submissives. Individuals who move between top/dominant roles and bottom/submissive roles—either periodically within a relationship, or from relationship to relationship—are known as S/switches.

BDSM is often practiced within the context of a limited and defined encounter known as a BDSM scene. Such scenes often have ritualistic aspects, complete with modes of behavior, forms of address, codes of conduct, dress codes, and many other aspects of theater and role playing. As such encounters are often—but not always—at least partly sexual in nature, people outside of BDSM have a tendency to view it as a form of "kinky sex".

Some participants incorporate aspects of BDSM into their everyday relationship(s) with their partner(s), especially those who practice dominance and submission or power exchange (especially Total Power Exchange). For these individuals, BDSM is part of their lifestyle and in some discussions is referred to as "The Lifestyle".