Old colloquialism, for a prostitute. In use since the 16th Century.
Modern times usually has the connotation of merely someone who is considered a sex object, usually a woman.
It assumes there are no other reason for being with that person, other than to satisfy their sexual needs.
With other qualifiers, has been used to indicate those who are not of legal age.
U.S. gay slang, refers to it as a delicacy for chicken hawks, that being older males.