"BDSM" is an umbrella term for certain kinds of erotic behavior between consenting adults, encompassing various subcultures. Terms for roles vary widely among the subcultures. "Top" and "dominant" are widely used for those partner(s) in the relationship or activity who are, respectively, the physically active or controlling participants. "Bottom" and "submissive" are widely used for those partner(s) in the relationship or activity who are, respectively, the physically receptive or controlled participants. The interaction between tops and bottoms — where physical or mental control of the bottom is surrendered to the top — is sometimes known as "power exchange", whether in the context of an encounter or a relationship.