Through flood and through fire

What's the difference between a fairy and an elf? I read about it, but it still feels totally ambiguous. I think, there should be a difference, but it feels like everybody else is just messing everything up. The case: I'm currently drawing a picture which features a girl who should be a fairy. I thought. With Titania as her fairy queen. But I'm German and in German "fairy" is usually translated to "Fee", but Titania is not called "Feenkönigin", but "Elfenkönigin", which I would translate back into "elven queen" ... So what now?! Makes no sense! Just as bad as bra sizes.

Above are sketches of ACEOs I want to sell at the upcoming Connichi. No danger of faeries here.

yaku~