Gold
Gold coins are the main currency in UO, it can be used to buy items from NPC vendors, or players.
You can find gold on most monsters, or NPCs will pay you money if you sell certain items to them.
Gold is also found in treasure chests, or as a reward for doing certain quests (though usually in relatively small amounts).
Large amounts of gold can be transformed into checks to save space.
Acquiring gold from monsters in great quantities is sometimes referred to as "gold farming."