I is for intersex, which is when the body didn't develop right during pregnancy and the individual can have combinations of male and female secondary sex organs, and outward characteristics may not match their chromosomal definition of gender. You may also have heard the term hermaphrodite to describe this medical situation, though I think that's more often used to describe animals.

A is for asexual, which are people who don't enjoy or get the appeal of sex, and will not have sex in any romantic relationships. Could think of it as someone who's libido is just always at 0 and they have no real desire to engage in sex with anyone of any gender.

Q is for Queer, which encompasses a general connotation of non-heteronormative sexual preferences, but isn't explicit in what those preferences are.