My kid and I am just learning how to cook, and I keep seeing these
recipes that call for "an egg".
http://www1.picturepush.com/photo/a/...g/12981834.jpg

For example, we were making onion rings today and found this:
http://www.bhg.com/recipes/how-to/co...e-onion-rings/

Seems to me, except for the seasoning, the egg & milk aren't
any better or worse than equivalent amounts of water ... but
maybe I'm missing something.

QUESTION: What 'does' the egg actually do in these recipes?