A trustworthy source has told Wired that Amazon will launch its AppStore for Android on 22nd March which happens to be this coming Tuesday.
First thing you need to know about this new AppStore is that it is different from the Android Market as the apps will be first reviewed by Amazon officials and only after their approval will they go live for public download. This as you know probably is different from Google's approach for Android Market where just about any app can make themselves available for download.
Next thing to educate yourself is the possible ways by which you can purchase the apps. You can buy apps directly from Amazon.com or if you wish you could download it using Amazon app for Android on your smartphone or tablet.
Here is an interesting Amazon AppStore feature. links that point to other apps should only point to those that are hosted on Amazon's app marketplace. So Yes, an app can't point to another app located in Google's very own Android Market. Amazon is likely to sell apps, which will also feature Rovio's Angry Birds Rio, on a cheaper price in comparison to the Android Market which might present a threat to the search engine giants.