A heterosexual person is attracted to people of the opposite sex. Boys who like girls and women who like men are heterosexual.
Being heterosexual has long been considered "normal" in our society. When you think of a married couple or parents, it's usually been a man and woman — in other words, a heterosexual couple. However, being heterosexual is only one sexual orientation. Other people are gay, or homosexual. Our culture is slowly starting to accept that heterosexuality isn't the only acceptable sexual orientation. Another word for heterosexual is straight.