BDSM is only done between consenting adults. This is what deliniates it from criminal behavior. If there is no consent it is not BDSM. Consent can be withdrawn at any time by either the submissive partner (see below) or the dominant partner (also termed the Bottom or the Top).
BDSM is only done in as safe a manner as possible. The reason that it is only for adults is that adults are aware of the risks they are entering into, as small as those risks are. The people participating in a BDSM scene or relationship know what they are getting into, how they are going to bring the scene or relationship into being and how they can protect themselves if something goes wrong.
BDSM is aware of the difference between our fantasies and the reality of what we can do to bring those fantasies to life. Some fantasies are too dangerous, or too unhealthy to bring into reality but with a little work a simulation of this fantasy can be created which will make it safe.
BDSM is about turning our sexual fantasies into real experiences. This can extend from what happens in the bedroom, or other rooms in the house, to lifesyle changes which can make it feel like we are living those fantasies 24/7. This is not to say that BDSM brings these fantasies into real life, but only that we can make is seem like those fantasies have been extended into real life.
BDSM is also about a Power Exchange between two people. One cannot exchange power with powerless people so, while some members of the community call themselves submissive or even slaves, this doesn’t mean that they are powerless. Many very powerful people are submissive in the BDSM world and the fact that they can withdraw their consent at any given moment allows them to reclaim that power. While the Power Exchange would seem to flow from the submissive to the dominant, it also flows the other way, as the trial the submissive is living often gives them the power they need in their real life.
BDSM is not about violence. Violence is non-consensual. It is one person imposing his or her needs upon another person without that person’s consent. A victim of violence has had their power taken from them involuntarily. In a BDSM scene both participants should walk away from it feeling better about themselves than when they started the scene.
BDSM is the universal solvent of sexuality. It can encompass any kind of sexuality, from simple missionary fucking, where one would have to be aware of BDSM to see the power exchange going on, to all he various different fetishes, to determining the way one conducts one’s relationships.
BDSM is about sexuality. While some of the ways BDSM manifests itself are not explicitly sexual, the aim is always to enhance one’s sexual life. Simply living a 1950’s husband dominant, wife submissive lifestyle, without the sexual components of BDSM is not enough.
I suppose it is rather longer than you asked for, but there it is.
qui bene amat bene castigat