I have absolutely no idea what this API is going to do, but I am excited about its potential.
What it does it allow users to build applications using the Envato API . Based on what Envato allows or builds into their API , will allow developers to work that stuff into an application, RIA , website, iphone app, etc.
So for instance you may be able to download an AIR app that will track all of your comments, or your sales, or possibly reply to comments/forum threads right from the app. Its very exciting!