http://en.wikipedia.org/wiki/Courtesan
Today, the term courtesan has become a euphemism to designate an escort or a high-class prostitute. A courtesan offers her charms and sexual pleasures, generally to people of substantial wealth, in return for money. She differentiates herself from other prostitutes by tending to service a few long-term clients, depending on her ability to seduce on a number of levels.