The term "renting points" can be confusing, because you don't actually get any points.
What happens is that a DVC member makes a reservation for you at one of the Disney Vacation Club resorts, using their points. You pay per point, by the number of points it takes to make the reservation at that particular resort, for the particular room type and size that you want, in the time of year you want to go.
The three most important things to know are:
1) You'll need to pay most, if not all, of the cost at the time the member makes the reservation. And most rental transactions are not changeable and not refundable. If you think you'll need to move your dates, or you might want to switch resorts, or there's a fair chance you'll have to cancel....renting is probably not for you.
2) As with most timeshares, you'll need to book much earlier than you do with a hotel. Members can start booking their home resorts at 11 months out, and for certain resorts and certain times of year, if you don't do that, there won't be any availability.
3) As with most timeshares, you will not get daily housekeeping unless you pay an additional fee for it. Villas are fully cleaned between guests, of course, but housekeeping services are limited during your stay.
It it cheaper? If you're comparing to the cost of booking the same villa through Disney, then yes, it usually is. Sometimes significantly. If you're comparing to the cost of a moderate or a value, no.