Amazon Coins is a virtual currency that you can use to buy apps or supported apps that use the Amazon SDK to make in-app purchases. The big different between Coins and just using your credit card is that you can always get discounts. Speaking of which, Amazon is currently running a promotion where you can save 20% of all Coin bundles for a limited time.
Michael Kozlowski is the Editor in Chief of Good e-Reader. He has been writing about audiobooks and e-readers for the past ten years. His articles have been picked up by major and local news sources and websites such as the CNET, Engadget, Huffington Post and Verge.