What Is Anorexia?

So today my friend asked me, "What's anorexia?"
And I just looked at her.
And looked some more.
"What?" she asked, eyes wide.
I couldn't tell at first if she had suspected something--but if she had, she would've had to do some research or at least known something about the disorder. But she didn't. She legit didn't know. She told me about how for her creative writing project she wanted one of her characters to have anorexia. But first she had to know what it was. She honestly had no idea how relevant her question was to me.
So I explained it, put reason where there was none, described the writhing, chaotic mess of my own self-loathing in neat, tidy words. Little boxes overflowing with long vocabulary. I kept it as seperate from myself as I could, rearranging my features into a mask of passivity. I was detached as I recited what could have been a dictionary definition. She nodded, jotted some notes, and thanked me.
And that was all.
In a weird way, it felt like I'd confessed--when I obviously hadn't.
She doesn't know. She doesn't know anything at all.
Clueless. Ignorant. Part of it hurts, the other part laughs with bursts of superiority.
She doesn't know anything.