Domination and submission is a lifestyle. Often it is seen as a form of erotic play. Usually two people do this. With this lifestyle or context, one of the two people has the dominant role. He or she can tell the other (called submissive) to do things. The submissive has to obey. The roles are usually agreed on beforehand. The submission is voluntary. Sadomasochism may be seen as a variation of domination and submission. A person who plays both roles is called a switch.