Dominance and submission

Dominance and submission (also called D&s, Ds, and D/s) is a set of behaviours, customs and rituals involving the giving by one individual to another individual of control over them in an erotic episode or as a lifestyle.
Physical contact is not a necessity, and it can even be conducted anonymously over the telephone, email or other messaging systems. In other cases, it can be intensely physical, sometimes traversing into sadomasochism. In D/s, both parties take pleasure or erotic enjoyment from either dominating or being dominated.
Those who take the superior position are called Dominants, Doms (male) or Dommes (female), while those who take the subordinate position are called submissives or subs (male or female). A switch is an individual who plays in either role. Two switches together may negotiate and exchange roles several times in a session. "Dominatrix" is a term usually reserved for a female professional dominant who dominates others for pay.

Dominance and submission, and the inner conflict and surrender connected with these are enduring themes in human culture and civilization. In human sexuality this has broadened to include mutual exploration of roles, emotions and activities which would be difficult or impossible to do without a willing partner taking an opposing role.
A safe word is usually given to the submissive partner to prevent the dominant from overstepping physical and emotional boundaries. The safe word is especially important when engaging in verbal humiliation or playing 'mind-games' because the submissive may not be aware of an emotional boundary until it is crossed. If an emotional boundary is breached and the safe word called, the dominant should cease all play immediately and discuss the emotional breach with the submissive in a tender and understanding manner.

 Negotiating limits in advance is also an important element in a D/s relationship.It is important to note that for a safe, sane and consensual environment to be maintained, all participants should have a safe word of which the other is aware; this includes the Dominant partner. While it may not seem so from the outside, Dominants will also have limits and boundaries of their own, and should not only have a safe word, but be comfortable calling it if their own limits are exceeded. This includes cases where the dominant may feel things have gone too far, and are uncomfortable continuing. As with a safe word call from any other, it should herald the stopping all play and a recuperative discussion between the participants.D/s may be ritualized or freeform. It is usually a negotiated lifestyle, with people discussing their wishes, limits and needs in order to find commonality. A D/s relationship may be sexual or non-sexual, long or short term, and intimate or anonymous. Most adherents search for the essential intensity, trust and intimacy that are required to make any deep relationship possible.

D/s participants often refer to their activity as play, with an individual play session called a scene. In addition to dominant and submissive, a switch is a person who can take either role. A scene between two switches can involve trading off the dominant or submissive roles, possibly several times. 
The term vanilla refers to normative ("non-kinky") sex and relationships, the vanilla world being mainstream society outside of the BDSM subculture. The term comes from vanilla ice cream being considered the "default" flavour and uninteresting.