I would say it's someone who's interested in/knows a lot about/talks or blogs about food. 'a foodie' is a kind of casual/fun expression, though - not for a professional food critic or something. :)

Yes specialist in cooking, and it mean also a person Who is eating different kind of food.

I might ever heard foodie, but I'm not really sure what it really means or how to use it. If you are specialized in food, like all kinds of activity involving food? I'd say you're a Food Master, or a Foodman, or probably a Food Hero. Referring to the word Junkie, it probably came from Junk. In my country, Junkie means a person whose attitude and appearence is close to Junk. Therefore if you say someone is Foodie, then it prolly means that the person smells like food and he could have some sort of ability to draw people's hunger once looking at him?