They come in a cardboard box, with a plastic tub and a bag of saltwater inside, in addition to the sealed meal. You take everything out, pour the saltwater onto the chemical element in the bottom of the tub, put the meal back in the tub, and slide everything back into the box for 15 minutes. Watch the steam come out. Self-heating, wide variety of meals, easy storage.
I've used them for years for camping, for meals at outdoor concerts, and for emergencies (like when my wife visits her family in CA).
"Don't overlook Heater Meals
http://www.heatermeals.com/
for storage for emergencies. I'm still using my Y2K stock, and they're in good shape...I've used them for years..."