A refrigerator swap is where you sign up on one of the threads to use the fridge during your stay. You retrieve it from bell services at your hotel, plug it in in your room, and return it to bell services with the name and reservation of the person using the fridge after you. It's very simple, and it's free!!
If you are staying at a value resort where a fridge cost $12 per night, it's definitely a way to save some money.