Sexual orientation refers to an enduring pattern of emotional, romantic and/or sexual attractions to men, women or both sexes.
Sexual orientation also refers to a person's sense of identity based on those attractions, related behaviors and membership in a community of others who share those attractions. Research over several decades has demonstrated that sexual orientation ranges along a continuum, from exclusive attraction to the other sex to exclusive attraction to the same sex.
However, sexual orientation is usually discussed in terms of three categories: heterosexual (having emotional, romantic or sexual attractions to members of the other sex), gay/lesbian (having emotional, romantic or sexual attractions to members of one's own sex) and bisexual (having emotional, romantic or sexual attractions to both men and women). This range of behaviors and attractions has been described in various cultures and nations throughout the world. Many cultures use identity labels to describe people who express these attractions. In the United States the most frequent labels are lesbians (women attracted to women), gay men (men attracted to men), and bisexual people (men or women attracted to both sexes). However, some people may use different labels or none at all.
Sexual orientation is distinct from other components of sex and gender, including biological sex (the anatomical, physiological and genetic characteristics associated with being male or female), gender identity (the psychological sense of being male or female)* and social gender role (the cultural norms that define feminine and masculine behavior).
Sexual orientation is commonly discussed as if it were solely a characteristic of an individual, like biological sex, gender identity or age. This perspective is incomplete because sexual orientation is defined in terms of relationships with others. People express their sexual orientation through behaviors with others, including such simple actions as holding hands or kissing.
Thus, sexual orientation is closely tied to the intimate personal relationships that meet deeply felt needs for love, attachment and intimacy. In addition to sexual behaviors, these bonds include nonsexual physical affection between partners, shared goals and values, mutual support, and ongoing commitment.
Therefore, sexual orientation is not merely a personal characteristic within an individual. Rather, one's sexual orientation defines the group of people in which one is likely to find the satisfying and fulfilling romantic relationships that are an essential component of personal identity for many people.
American Psychological Associate - Sexual Orientation