Amazon Coins is an easy way for Kindle Fire customers to spend money on developers’ apps in the Amazon Appstore, offering app and game developers another substantial opportunity to drive traffic, downloads and increase monetization even further.

Amazon will give customers tens of millions of dollars’ worth of Amazon Coins to use on developers’ apps in the Amazon Appstore—apps and games must be submitted and approved by April 25 to be ready when Amazon Coins arrive in customers’ accounts. (Source)
Amazon calls the Coins an important step to create the “most complete end-to-end ecosystem for building, monetizing and marketing their apps and games.”