The terms "homosexuality," "heterosexuality," and "bisexuality" really don't apply to reality. A vast amount of people have some kind of "same-sex" sexual experience - whether it be actual sex or a crush or a fantasy - and still function as "straight." These terms really only work for the people who use them to malign people. A "same-sex" experience works like the "one-drop rule" of race: just once is enough to change how you're treated.
Apart from the Kinsey-esque proportioning of sexual experience in humans is the difference between genitalia and functioning. When you pass people on the street, you probably have no idea what genitals they have, what chromosomes they have, etc. You probably don't even know your own chromosomes! And you don't know with whom they have sex, about whom they're thinking when they have sex, etc. Biology and actual sex have nothing to do with anything...until you're caught at it.
What really matters, more than biology and more than one's sexual experiences, is how one functions in reality. A masculine, woman-identified female functions very differently from a feminine intersexed person who passes as a woman. And how could you possibly ascribe "homo-", "hetero-" or "bisexual" to either of those people? "Man" and "woman", "male" and "female" not only leave out people who don't fit into those two categories, but they also exclude more finite ways of being that affect people in more significant ways.
Just three terms aren't enough to cover everyone...but the government, military, religious institutions, advertising agencies, and many others in positions of power use those three terms - if we're lucky - and two terms of sex/gender. In reality, these terms mean very little. Hell, the handkerchief-flagging system is more efficient than check-boxes!