A prostitute is someone who gets paid to have sex — the word usually refers to a woman, but there are male prostitutes as well.
These days a prostitute is often called a sex worker, and there are many slang words, such as hooker and whore, that mean the same thing. A prostitute works for a pimp and her customers are called johns. You could say a woman is prostituting herself, or that the pimp is prostituting her. Sometimes people who hate their jobs feel like they're prostituting themselves, even though no sex is involved.
