the term bisexual is used in the context of sexual preference rather than the context of sexual identity.

people can be heterosexual (have a sexual preference for members of the opposite sex)
people can be homosexual (have a sexual preference for members of the same sex)
people can be bisexual (not have a strong homosexual or heterosexual preference)

sexual preference is about what kinds of people one is attracted to / prefers to have sex with.

though... there is a confusion of terms admittedly. and some groups purposely reject some of the terms because they don't like the way they are defined.

e.g., sometimes bisexual is defined as someone who has 'indiscriminate' sexuality. some people object to this because they feel it has connotations that people who are bisexual are willing to have sex with anyone and everyone.

i think that intersex / hemaphrodite might be the terms for people who have indeterminate sexual identity with respect to the current black and white 'male' and 'female' categories.