The resulting consent and understanding is occasionally summarized in a written "contract", which is an agreement of what can and cannot take place.Use of the agreed safeword (or occasionally a "safe symbol" such as dropping a ball or ringing a bell, especially when speech is restricted) is seen by some as an explicit withdrawal of consent.
For the medical condition in which pain/humiliation is required for sexual arousal and causes distress or impairment, see Sexual masochism disorder.
BDSM is a variety of often erotic practices or roleplaying involving bondage, discipline, dominance and submission, sadomasochism, and other related interpersonal dynamics.
Some have a policy of panties/nipple sticker for women (underwear for men) and some allow full nudity with explicit sexual interaction allowed.
The fundamental principles for the exercise of BDSM require that it should be performed with the informed consent of all involved parties.
The terms "top" and "bottom" are also used: the top is the instigator of an action while the bottom is the receiver of the action.