A ‘Switch’ is someone who changes roles depending on the situation/partner(s).
People can assume the Dom/sub roles during other types of play, but they can also be reversed, for instance the Sadist acting on the Masochist’s instruction, who in that instance would be considered the Dom. D/s refers to psychological power-play, where the Dominant partner controls or has power over the submissive. S&M is about deriving sexual pleasure from pain, where the Sadist inflicts pain upon the Masochist (what I would consider ‘sensation play’, the sensation being pain), while B&D is play that involves physical or psychological restraints or punishment.
Sadism is pleasure in the infliction of pain or humiliation upon another person, while masochism refers to gratification from receiving the same.
Sadomasochism or better known as S&M or SM.