I'll give you the short version, then, and let you ask questions.
The judges are what run this place. They used to be deities, but they lost their followers; now they bring people in to provide what they need. Fear, pain, communication, beauty, mischief... it varies, depending on the judge. They use us for what they need, and they torture us and kill us when it suits them. In return, the promise was that we would be granted a wish for playing along.
But there's another thing here, too, that's similar to the judges. It's the Old Man- the earth. Did Aoi mention it?