An early 20th century post card documents the problem of unwanted pregnancy.
Sex education is telling people about sexual intercourse. Usually, parents tell their children when they reach puberty. This usually includes things like how to make babies, how to protect against unwanted pregnancies, and how not to get any of the sexually transmitted diseases there are. In many cultures speaking about sex or sexual education is a taboo.
Some level of sex education is also done in school; in many places, the government passed laws that say that sex education must be done in school. Some parts of sex education vary by culture, e.g. the moral and ethic aspects.