Role-playing refers to the changing of one's behavior to assume a role, either unconsciously to fill a social role, or consciously to act out an adopted role.
Many people regard role play as a means of overcoming sexual inhibitions. It may take place in the real world, or via some form of cyber domination format--allowing for physically impossible or intensely taboo erotic interests to be enacted without having many of the typical real world ramifications that may be humiliating.
How seriously the play is taken depends on the people involved, and the scenario may be anywhere from simple and makeshift to detailed and elaborate, complete with costumes and a script. Nearly any role could become the base material for an erotic experience, and there is no limit to what objects an individual could consider sexual.
It may, for example, involve wearing of a costume which is regarded as erotic, such as a miniskirt and stockings or preferred characterization, or one or both partners being nude. It may involve elements of D/s and or bondage, either being restrained oneself or a partner being restrained, aspects of SM, humiliation and other various disciplines.
The popularity of the Internet has also allowed for online sexual encounters, known as cybersex, which may involve roleplay.