Short for Adobe Integrated Runtime, AIR is a new Adobe environment that is an extra layer of software that allows the same program to run on different operating systems and hardware, much like Java runs. AIR allows applications to be installed on the local operating system and accessed from the desktop just like the other applications that the desktop user runs. At the same time, AIR applications can access online information. AIR applications can run either online or offline, but is aimed at Web developers and its primary use is to enable Web applications and Rich Internet Applications (RIAs) to be deployed to the desktop. The eBay Desktop and Google Analytics are examples of prototypical AIR applications.
See Rich Internet Application (RIA).
See also "Building Desktop Applications For The Web With Adobe Integrated Runtime" on Developer.com.