Concubines are essentially mistresses. Historically a concubine would have been engaged in a long-term relationship – marriage in all but name - with a man of higher social status who they could not marry. The arrangement was sometimes voluntary, as it would provide a woman with an easy and secure living. In Ancient Rome and China, concubines had legal status.
Courtesans were female courtiers: people who attended the monarch’s court when such places were the centre of government. As royal marriages were primarily intended to preserve bloodlines, monarchs would seek out relationships with others residing in their court. In Renaissance times, the Italian term cortigiana came to mean ‘ruler’s mistress’. Such women were often well-educated, adept in the arts of dance and music and held in high regard. Today, the term is often used euphemistically in referring to high-class prostitutes.