Neuroscience and sexual orientation
Sexual orientation is an enduring pattern of romantic or sexual attraction (or a combination of these) to persons of the opposite sex or gender, the same sex or gender, or to both sexes or more than one gender, or none of the aforementioned at all. The ultimate causes and mechanisms of sexual orientation development in humans remain unclear and many theories are speculative and controversial.
Source: Wikipedia — Neuroscience and sexual orientation (CC BY-SA 4.0)