Sexual intercourse
Who people like to have sex with depends on their sexuality. Men who like to have sex with women, and women who like to have sex with men are heterosexual or straight. Men who only like to have sex with other men, and women who only like to have sex with other women are homosexual or "gay". A different word to describe a woman who only likes to have sex with other women is "lesbian". Some people like both men and women, which is called being bisexual. Others do not feel sexual attraction at all, and are referred to as asexual.