The AIR platform, which began on the desktop, stands for Adobe Integrated Runtime. It's a platform for users to run rich Internet applications locally, much like a typical software application. In that same vein, AIR apps can take advantage of the hardware they're running on in ways that Web apps in the browser sometimes can't.
This new app comes without a built-in directory of applications that users can install. Instead, it works much like it does on the desktop, with any AIR apps the user encounters in the browser being able to be installed locally. Those applications then run on top of the runtime. Developers also have to do a bit of fine-tuning with their AIR applications, which can be done within Adobe's Flash Builder toolset.
Adobe says that AIR will eventually come pre-installed on Android devices, and now that AIR is available, attempting to run an AIR app on an Android phone will take you to a page with a download link for the application. In the meantime, getting AIR on your device has the same requirements as Adobe's Flash plug-in, which is: a phone running at least version 2.2 of the Android OS (a.k.a. "Froyo") as well as 256MB of RAM and an ARMv7-A processor.
To download AIR to your Android device, you can either snap a picture of, or click on the QR code to the right if you're reading this post on your phone.