It is Disney's points based version of a time-share.
You need to read the stickies at the top of these pages, read multiple of these threads, and then read some more.
You need to understand the following terms:
Points
ROFR
UY
studio, 1 & 2 bdrm, & grand villa - and know the differences
ending date of your contract
MF
resale vs direct purchasing
After you have all these terms down; read some more.