Hi Darryl,
Some of these questions are kind of hard to answer, because BDSM isn't any one thing. It's more of an umbrella term that encompasses a wide variety of kinks and lifestyles that tend to include some level of temporary or permanent power exchange. as such it's tough to accurately describe the choices, motives, or lifestyle of any particular individual. Also, different people have different terminologies, so for example "sub" may have many shades of meaning based on who you're talking to. That aside, I'll take a shot at answering your question.

Ok so...doms and subs are, in the loosest sense, people who enjoy being in relationships with some level of power inequality. Doms prefer to be the people with greater power in the relationship, subs prefer to be the people with less power. "Owned" is another one of those words that has a lot of different shades: it can mean anything from a near-traditional girlfriend to a slave who has given up all of her rights and decisions to her owner/master.

A person might _choose_ to be owned for a variety of reasons, but some people do feel freedom, tranquility, or excitement in having responsibility for their decisions removed from them and taken on by someone else. Other people feel a strong desire to be of service to someone else. Still others enjoy physical pain, or humiliation, or any of few dozen other things.

Regarding brutality, ethical people in BDSM use the term SSC (Safe, Sane, and Consensual) to describe ethical interactions and play. Safe means that the activity isn't going to be permanently harmful, and that safety precautions such as safewords that can stop play immediately are in place. Sane means that it's not completely irrational and that the people involved are of sound mind. Consensual means that everyone agrees beforehand, with full foreknowledge, to the types of activities that are going to happen (and, by definition of consent, that they are grown ups).