Amazon launched its own Amazon Appstore in March 2011 as an addition and alternative to the Google Play Store. The Amazon Appstore - unlike Google Play - already comes pre-installed on all Android based Amazon Devices such as the Kindle Fire. Despite being pre installed on all Amazon Devices - The App Store and Amazons Free App of the Day offer is avilable for download to all Android Users and devices.
While Amazons Appstore might have less apps available at the moment than Google's Play store - currently over 675000 - each app is individually tested before it is approved in the store, drastically decreasing the chance of downloading malicous software.
