The Elder Scrolls Online doesn't contain an in-game auction house. Instead, players can buy and sell items through guild stores. However, ZeniMax Online has come up with a way for players to participate through in-game trading.
According to a post on the ESO forums, players will be able to trade, buy and sell goods and services through an online marketplace instead. This will not only, according to the developer, keep the game's economy healthy, but will encourage socialization.
"You don't necessarily want to do a global auction house for a game with one giant server because that generally leads to all the best gear being available at very, very cheap prices," according to gameplay designer Nick Konkle. "A lot of times that can trivialize the game.
"You cannot have a healthy economy when there are no restrictions on getting the best stuff in the game."
So, if you want to sell your wares or buy something crafted by a player or any other sell-able item in the MMO, you will either have to visit the marketplace linked above or join a guild.