Sexual orientation is forms of attraction to people. There are many different groups. Some examples are: attraction to a different gender (heterosexuality), attraction to the same gender (homosexuality), attraction to more than one gender (bisexuality), and no attraction any gender (asexuality).
The groups are part of sexual identity. Some people use something such as pansexual or polysexual. Other people use nothing at all. Androphilia and gynephilia are an alternative to the gender binary in homosexual and heterosexual. Androphilia is attraction to a man or masculinity (any quality or behavior linked to a man). Gynephilia is attraction to a woman or femininity. Sexual preference overlaps with sexual orientation but is different. A bisexual person may like one gender more than another. Sexual preference may also give the idea of a degree of choice. The scientific consensus (position in the community of scientists) is that sexual orientation is not a choice.
Scientists do not know the exact cause of sexual orientation. There is some evidence of genes involved, however the main theory is related to hormones when a baby is growing inside the mother. For males, there is better proof of a biological cause of sexual orientation than social causes. In women, there is some evidence that social factors may play a small role.
Sexual orientation is important in biology, psychology, anthropology, history, and law.