Perhaps you should ask in the
DVC-Operations forum...
Brief overview (I just purchased):
You buy a certain number of "points", which are allocated to you annually. Those points belong to a particular resort (you can potentially get points from different resorts, but that gets complicated) with which you can make reservations up to 11 months out, but you can book any DVC resort up to 7 months out, all subject to availability.
Each room type (studio, 1BR, etc.) and class (standard, preferred, etc.) costs a different number of points per night, and vary during the season, so depending on what days and what time of year, you use your points to book your stay in your desired room.
You can also trade your points for rooms at other Disney resorts (but its expensive), or other resorts around the world (through agreements with other timeshare organizations).
More questions can be answered in the DVC-Ops forum (where I think this thread may get moved...)