Some people use the word queer as an umbrella term to describe any non-normative sexualities and gender expressions, especially homosexuality, bisexuality, transgenderism and intersexuality, but also sometimes BDSM, fetishism, prostitution, and polyamory. Various paraphilias may be seen as a kind of sexual orientation, although they are usually considered orthogonal (unrelated) to the gender-based categories of sexual orientation, and are seen as existing in addition to such orientations.However, some paraphilias may be a more significant focus of an individual's sexuality than the gender of partners.The terms heterosexual, homosexual, bisexual, monosexual, asexual and autosexual can all be used to describe phenomena unrelated to sexual orientation, for instance in phrases like "a homosexual act".Following from the 1960s and 1970s sexual revolution in the West, there has been an explosion of open discourse on sexuality by sexual minorities.It was used in the 20th century by gay rights advocates who sought to promote the view that each person should have the right to seek out the partner they prefer, whether of the opposite sex, the same sex, or both sexes.
Markers of sexual orientation include self-labelling, actual sexual behaviour, sexual fantasy, and a pattern of erotic arousal – a "pattern" being most accurately identified when genital engorgement with blood is measured in response to homoerotic material with penile plethysmography or vaginal photoplethysmography .
People are typically classified as heterosexual if their sexual focus is primarily people of the opposite sex/gender to their own, homosexual if it is people of the same sex/gender, and bisexual if it is both men and women.
The less formal terms "straight", "gay", and "lesbian" are more commonly used by people to describe themselves and their friends and family, or to emphasize sexual orientation as a social identity.
”Sexual orientation“ is also a legal term that has a meaning developed through case law that is separate from the meaning used in other fields.
It is the most common term used in laws that prohibit discrimination based on homosexuality, heterosexuality and bisexuality.