Merchants are NPCs that buy and sell items. They can usually be found in shops such as the Market District of the Imperial City. Others can be found in inns, roaming Cyrodiil, or as Guild members. The latter only trade items if the hero is a member of their respective guild. Merchants have a limit of how much they can spend in one transaction, though you can sell items to them over and over again, as they never run out of money.