Coins

 are the currency of Terraria. They despawn after 12 minutes.

Update Info
1.2.4

Coins can now be placed in the background.

v1.2.3.1
 * Platinum coins now stack to 999.

Obtaining coins
Players can obtain coins by killing monsters, destroying pots, finding them in chests or selling items to Merchants. With coins you can purchase items from the Vendors. A stack of up to 100 of any single type of coin takes up one inventory slot. However, there are reserved slots for coins, on the far right side of the inventory that may be used instead.

Coin types
Coins come in different types. They can be crafted to and from other coin types without loss of value. It takes 100 coins to upgrade, and you get 100 coins of lesser value when one is "broken" or downgraded.

Platinum is the most valuable coin available. When Platinum coins are being spent, they downgrade to Gold Coins.

Death penalty
Upon death (in Softcore Mode), half of all the stacks you have of coins in your inventory will be dropped (rounded up if the number is odd). For example, if you have 1 Gold coin in one stack, you will drop it, but if you have 12 coins you will drop 6. You will still drop half of your coins if you commit suicide with self-thrown explosives.

Storage
Coins have their own storage slot but can also be stored in the normal inventory like anything else. Coins can be stored in a Chest, Safe, Piggy Bank, Barrel and any other form of storage. Coins placed in any stationary container will not be lost when you die. It is advisable to place all your coins in a Chest, Safe or Piggy Bank every time you return to your home or before fighting a boss.

Farming
You can farm coins by linking active stone blocks to an electric current (e.g lever or 1 second timer ) and placing any kind of chest with anything inside the chest and sell the chests to the Merchant for gold and silver coins. (no longer works in 1.2.4)

Money Making Tips
There are many ways to make money in Terraria, some of them easy to setup, with a lower profit, others, more difficult to setup with a much higher profit. Most ways consist of farming, or lava traps using statues. An easy pre-hardmode way to rapidly gain money is to sell your ores. Once you defeat the wall of flesh, copper, tin, iron, lead, silver, tungsten, gold and platinum won't be of nearly as much use. Selling them can yeild hefty amounts of gold coins, but another way is to farm the Eater of Worlds and the Eye of Cthulhu for demonite. Say you fought the Eye of Cthulhu twice, it would yeild somewhere around 30 bars of demonite or more. If you sold those 30 bars of demonite you'd get 9 gold coins and 60 silver coins. Boosting off these bosses is also very simple. For the Eater of Worlds just spawn it while you're in a condensed room, then spam a spell like water bolt, as long as you keep your health up you'll defeat it in seconds. For the Eye of Cthulhu one way of defeating it rapidly is to use the Magic Missile or the Book of Skulls to fire at it until you run out of mana, then while you're waiting to recharge use a flail like the Sunfury or Blue Moon to keep dealing damage while evading its attacks.

Bugs

 * It was possible to keep one stack of coins on death by "holding" it with your mouse arrow right before you die, but as of the patch 1.1.1, mouse items drop normally.
 * You may also avoid losing coins on death by adding them to your trash and taking it out afterwards.
 * In the IOS version, if you take out coins from a chest, say 70 silver coins, and you have 30 silver coins, the stack turns into 100 and will not convert. This can be fixed by placing one coin into your hand, drop it out and then collect it.