In a nutshell:
Purchase
Vacation Club points - a one time expense of approximately $100 per point, minimum purchase 160 points
Pay
Maintenance Fees - every year, approximately $5.00 per point
Stay
at any DVC resort and "spend" your points on a variety of accomodations -point requirements vary depending on the size of the villa, the time of year, and the night of the week
Enjoy
prepaid deluxe accomodations at WDW every year for the next 35 - 50 years, depending on the resort you chose and the year it expires