Bisexuality is when a person experiences physical and romantic attraction towards people of both sexes. In other words, it is when a person is attracted towards both men and women.
It is distinct from homosexuality, which is when a person experiences physical and romantic attraction exclusively towards people of the same sex. And it is distinct from heterosexuality, which is when a person experiences physical and romantic attraction exclusively towards people of the opposite sex.
Bisexual people may experience attraction towards one sex more often than the other. For example, they may experience attraction towards people of the opposite sex 80% of the time, and towards people of the same sex 20% of the time, or vice versa.
Sexuality is enduring and immutable. A person’s sexuality does not change over the course of their life – indeed, it cannot be changed, either wilfully or forcefully. This means that a bisexual person cannot change to become fully heterosexual.