The way it works is this: You go into an instance, say Naxx, and everyone knows ahead of time that it is a "GDKP run," or a "gold run," or a "cash run." You down the first boss, and Webbed Death drops. The master looter then takes bids of gold on the item (this can be done via public chat or via an addon), and whoever bids the most gold gets the item. The person who wins then pays that amount of gold (some raids have minimum bids of, say, 100g) to "the pot," and the raid moves on. Another boss drops, another item drops -- usually all items, including recipes and mats, are auctioned off -- and another high bid goes into "the pot." Then, at the end of the raid, the pot is evenly split among all members. Everybody who joined in on the raid gets an even share of the bidded gold, including people who got no items, or the Mr. Moneybags who won them all.