IS THE DIFFERENCE BETWEEN A COURTESAN AND A MISTRESS THAT THE COURTESAN CHOOSES HER LOVERS?

In the book "MY LADY SCANDALOUS", author Jo Manning quoted Katie Hickman, who wrote a book called "Courtesans."

On page 2 of the hard back book it says that a Courtesan is a woman who accepts money for sexual favors but considers herself the lover of just ONE MAN.  Though many mistresses become courtesans, unlike prostitutes, a courtesan always chooses her patrons - for her pleasure too -  Her gifts are erotic pleasure, company, and conversation.