How does it work? Simple, really. It's rent to own, you pay a certain amount every month, and after whatever set time frame you choose, it's yours. Miss a payment, and they repossess, and you lose all the money you've been paying.
The catch is that you usually end up paying more than DOUBLE what the product is worth. It's just terrible from financial point of view. I really couldn't recommend that anyone use any rent-to-own company. If you can't afford to pay cash, a better option is a credit card.