Sex education is the introduction of sexual topics within an educational context. Almost all western countries have some form of sex education, but the nature varies widely. In some countries (such as Australia and much of Europe) "age-appropriate" sex education often begins in pre-school, whereas other countries leave sex education to the pre-teenage and teenage years.[citation needed] Sex education covers a range of topics, including the physical, mental, and social aspects of sexual behavior.

Human sexual behavior encompasses the search for a partner or partners, interactions between individuals, physical, emotional intimacy, and sexual contact. Some cultures discriminate against sexual contact outside of marriage; however, extramarital sexual activity is pervasive. Unprotected sex may result unwanted pregnancy or sexually transmitted diseases. In some areas, sexual abuse of individuals is prohibited by law and considered against the norms of society.

Heterosexuality involves individuals of different sexes.

Different-sex sexual practices are limited by laws in many places. Marriage laws may serve the purpose of encouraging people to only have sex within marriage. Sodomy laws were seen as discouraging same-sex sexual practices. Laws also ban adults from committing sexual abuse, committing sexual acts with anyone under an age of consent, performing sexual activities in public, and engaging in sexual activities for money (prostitution). Though these laws all cover same-sex sexual activities, they may differ with regards to punishment, and may be more frequently (or exclusively) enforced on those who engage in same-sex sexual activities.

Same-sex sexuality involves individuals of the same sex. It is possible for a person whose sexual identity is heterosexual to get involved in sexual acts with people of the same sex, for example, mutual masturbation in the context of what may be considered "normal" heterosexual teen development. Homosexual people who pretend to lead a life of heterosexuality are often referred to as living "closeted" lives, that is, they hide their sexuality in "the closet". The term "closet case" is a derogatory term used to refer to another homosexual that hides his or her homosexuality or bisexuality, and "coming out" or "outing" refer to making that orientation (semi-) public voluntarily, or by others against their wishes, respectively.

Eroticism is an aesthetic focus on sexual desire, especially the feelings of anticipation of sexual activity. It is not only the state of arousal and anticipation, but also the attempt through whatever means of representation to incite those feelings. Examples of erotism include erotic photography, hot girls posters or hot guys posters.

Some believe defining eroticism may be difficult since perceptions of what is erotic fluctuate. For example, a voluptuous nude painting by Peter Paul Rubens could have been considered erotic or pornographic when it was created for a private patron in the 17th century.