As some of you know, DH and I live overseas. We've been living outside the states for practically our entire lives, with short furloughs to the US occasionally. I've been living outside the US since I was 14, DH since age 7.

Well, we've just accepted a placement in Florida for 1-2 years, and being the research addict that I am, I'm trying to figure out life back in my own country.

Since we make very little money, I've been researching budget living in the US, and I'm curious about Costco. I keep hearing about it being a good way to save money.
I know it's a membership thing, which I don't really get. Will some kind American please explain it to this confused ex-pat?