Asexual is a terrible term - they have a sex, (Male or Female) - they just don't engage in sexual activity and have no desire to engage. Rather than having a low libido, they have an absent libido.
The Opposite of an Asexual would be a Nymphomaniac or someone with "Hypersexuality".
Should asexual be an orientation? Well, I suppose so. They're orientated to not finding anything sexually interesting. But you could look at it another way and say they have an absence of any orientation whatsoever.
As for how is it different from platonic love..... it isn't. You can love someone as an "asexual", but the entire thing about being "asexual" is that they do not have sexual feelings for others, thus all their relationships are platonic.
I'm not "asexual". I do have a low libido. I'm straight, but I honestly can't find it in me to seek out a relationship. I've never had a sexual relationship in my life, and while I am not opposed to the idea of marrying someone and having children, it's very low on my list of priorities. Sexual relationships as a whole are very low on my list of priorities, and because of that I fear that I would be a terrible husband for whatever girl who was unfortunate enough to marry me. I find the rest of the world so much more interesting than sex, movies and spending time with someone talking about how their day is. I like people, overall, but prolonged intimate contact with people is something I dread. I can hold a conversation for 30 minutes, but after that... I honestly just don't feel like talking anymore. I like spending time by myself. I like silence. I can go for hours without wanting to talk, and sometimes I prefer not talking and will actively avoid conversations.
