Sexual role-play involves two or more individuals acting out different roles in a sexual scenario. An example might be Doctor and Nurse. It can be any type of sexual fantasy.
It may be as involved as the participating individuals wish. Couples could choose to act the role-play out at a specific location, dressing up in detailed costumes or using different props. It may involve individuals assuming a participating role or that of a spectator. Technology has now brought about the possibility of sexual role-playing on the Internet as well, which many individuals and couples indulge in. Not quite the same as the real thing, but it allows someone with a specific fantasy fetish to indulge with a degree of anonymity.