Disney Vacation Club, its Disney's version of timeshare.
http://disneyvacationclub.disney.go.com/
Some love it, some like myself are not interested.
You have to pay a lump sum upfront then annual dues each year.
You also have to consider exchange rates as you pay in $'s the cost can increase greatly with a poor exchange rate.
Also consider deals Disney offer, like free
DDP, not available to DVC members, only way they can do it is to rent out their own points to take advantage of the deals.
If you 100% want to stay onsite every year or every other year for many years its possibly a good option, for us only way we will stay onsite is with a deal(recent years paid around £100/night OKW & free DDP or £70/night AKL savannah view with AP discount) no deals then we would rather stay offsite than pay DVC prices.
To give you example of costs our 16 nights stay next August at OKW would require 247 points annual dues for that amount of points would cost approx £750, initial cost would depend if you bought thru Disney or resale, anything from around $60 to over $100/point.
Lots of sites out there with info, one here
http://www.mousesavers.com/dvc.html
Read thru the DVC forums and other sites, its not for us but many enjoy being in it.