|Coin is earned by killing enemies or by selling items at Trading Posts located within each Outpost. Once earned, your Coin is safe. You do not drop it when defeated in combat.
The simplest option to earn Coin is by defeating Corrupted or Angry Earth enemies. In addition to Coin, they also may drop Talismans and Animorum, which are dropped by various enemies throughout Aeternum. These items have no other use, but they can be dropped if you die. This makes it a good idea to sell them quickly. Talismans and Animorum are unique in that they can be sold directly to the Trading Post.
Other items can be posted for sale, but another player must buy them for you to earn any Coin. Players can post an item for sale, which leaves the item available for others to purchase at a price set by the seller. Additionally, players can order an item, which offers to purchase a specific item for a price set by the buyer. You can sell instantly to these buy orders, or post an offer for your item in hopes that it will be purchased later.
For more info, the Systems Guide has a full chapter dedicated to the Trading Post.