And on a similar note, asexuals such as myself cannot understand sexuals.
As for the Bisexual/homosexual/heterosexual asexuals, you're thinking of bi-romantic, homo-romantic, hetero-romantic and so forth, who are people who feel no sexual attraction but feel romantic attraction towards others. Those who do not feel this either (I am afraid I shall fall into this category) are aromantic asexuals.
Also, there are multiple asexual types. Those who have no libido whatsoever, those with a libido but no sexual attraction, and those who experience sexual attraction towards objects only (certain fetishists, excluding body parts). I fall into the second, but my libido is so lacking that I might fall into the category of hyposexual (not a type of sexuality, just having a libido so minor as such for those who are hyposexual not to act upon their libido).
Asexuality is not to be confused with celibacy, where there is a conscious desire or attraction but the individual chooses not to act upon it. Neither should asexuality be confused with those with a sexual phobia or aversion, they may still experience sexual feelings but are consequently repulsed and do not act upon them due to fear of sex.
As you have probably guessed, I'm asexual. I too am a member of AVEN, and if anybody has any questions pertaining to asexuality, post them here and I can attempt to answer them. Without trying to view myself as arrogant, I'd like to think I know a fair bit about it... Even if I personally despise being asexual.