The sexuality is the set of emotional phenomena, behavior and practices associated with the pursuit of sexual pleasure, marking decisively to the human being in each and every one of the decisive phases of their development.
Sexuality encompasses biological, psychological, social and ethical aspects, which are part of how we perceive things related to sexuality. Sexuality encompasses sex, the identities and roles of gender, the eroticism, the pleasure, the intimacy, the reproduction and sexual orientation. It is lived and expressed through thoughts, fantasies, desires, beliefs, attitudes, values, behaviors, practices, roles, and interpersonal relationships.
Although before birth we have a sex and gender assigned, the sexuality of each person's identity may be different. There may be people who do not feel the biological sex that determines their genitals and who opt for hormonal or surgical treatment to change them (transsexuals). Also, people can be attracted to other people who can be of the opposite sex (heterosexual), of the same sex (homosexual, gay or lesbian) or to people of both sexes (bisexual).
The sexuality, although they live differently along the different stages of life, is part of everyone's life.
The sexual relationship begins when two people are physically attracted and a set of complex physical and emotional reactions take place, where feelings, affection, etc., are mediated by hormones responsible for the sensations of pleasure of the general well-being of the organism.
The sexual relationship tries to seek pleasant sensations, but they always have to be based on respect and responsibility, without any type of coercion, discrimination or violence.
Highly recommended documentary about transsexuality in children: The felt sex.