Elizabeth, I think Bill pretty much hit the nail on the head: It's self-defining!
In this forum, we use "foodie" as one of the "ranks" that people earn next to their name on posts depending on how many messages they've posted. We mean it affectionately, and in my mind, it's pretty simply stated as "someone who is passionate about food, not necessarily a glutton at all, but who is interested in eating and drinking well, perhaps in restaurants, maybe home cooking or possibly all of the above. But it's the passion, the caring and the interest that make the "foodie," not any silly requirement that one be willing to eat live cobra hearts or squirming tentacles.
Welcome, foodie!