Rick is most likely referring to an in-game auction house, rather than an auction in which he could sell the game sword for real money. Most MMORPGs (massively multiplayer online role-playing games) provide a way for players to sell items to each other in the game, using in-game money. This often comes in the form of an auction house, in which players will create a lot for their item and other players will bid for it, with the highest bid winning.
In RPGs players usually choose a ‘class’ for their character, such as warrior, mage or hunter, and each class is limited in what they can use. For example, a mage might not be able to wear full plate armour, but a warrior would not be able to use a magic staff. Added to this is the fact that different weapons will often aid the player in different ways. One sword might increase a character’s speed of attack, whereas another might increase his strength, or hit with extra fire damage. Different players will want different things from their weapons. Since the loot enemies drop is often random, the auction house allows players to sell what they cannot use and buy what they really need. These auction houses lead to the virtual world forming its own economy (see bookmark for page 12).