So what is BDSM?
It stands for Bondage discipline submission masochism. Bondage obviously means tying a person up. Discipline means things like spanking. Submission is pretty self explanatory and masochism means enjoying pain. When most people think of BDSM they think of a leather bound female dominatrix humiliating and disciplining a submissive man who is submissive to her desires 24/7. This is the popular image often displayed to the general vanilla public in comedies like Euro Trip.
But it doesn't have to be that way. Many couples enjoy aspects of the BDSM relationship without any submissiveness outside of the bedroom. Many couples also switch so that sometimes the girl is a dominatrix and the man a submissive while other times the man is a dom and the female his slave.