Well, it's renting points from a
DVC member. You would contact someone and ask to rent their points and they would call DVC and book it for you. The going rate is $10 - $12 per point.
It can be a GREAT savings over what you would pay if you booked the room yourself through Disney.
I rented my points out once last year to someone on the DIS. She got to know me and felt safe renting from me. There is a risk and trust involved (you pay the deposit and then the DVC member cancels your reservation for example) but if you go with someone with a high post count and references, you should be fine.
We agreed to everything and had a contract drawn up to make each other feel better. She gave me half the money up front and the other half 2 months before. I booked it right away and sent her the confirmation letter. She then called them to confirm and even made her special requests.
She got a studio at the Boardwalk for $90 a night which is a great bargain.
It would be up to you and the DVC member to decide the terms of the rental.
It would be wise to make your decision early on so that you have a higher chance of availability.
I would only rent if I was 100% certain I wouldn't be canceling as most will NOT return any deposits. They will try and reschedule for you but not refund the money.
The best place to ask your DVC questions is over on the DVC boards.