There's been a few discussions about it, but I can give you some info.
It starts every evening at 7:00 in the winter and 8:00 in the summer. It's by the Meadows Recreation Area. It's free!
It starts with a singalong around a big campfire where you can roast marshmallows (bring your own or buy their "kits" that include marshmallows & sticks). Chip & Dale visit during the singalong too!
Then, they show a full length Disney movie (2 in the winter) on the outdoor screen. There's bleachers and benches to sit on or you can bring lawn chairs or blankets.
There's a concession stand, called the Chuckwagon, that sells hot dogs, nachos, candy, ice cream, popcorn, etc, etc.
It's open to all WDW resort guests!