This is the software publisher's description.
The Adobe AIR runtime enables you to have your favourite web applications with you all the time. Since applications built for Adobe AIR run on your desktop computer without a web browser, they provide all the convenience of a desktop application.
Companies like eBay and AOL are using Adobe AIR to create exciting new applications that allow you to use their services on your desktop.
In short, Adobe AIR means applications that are easier, more powerful, and more fun to use.
Be safe on the web. Adobe AIR helps ensure safe installations by requiring digital signatures on each AIR application that identify the application and its creator before you install.
Installation of Adobe AIR is easy. You may already have it installed. If you don't, you will be able to install it automatically when you download an application that has been built to run on Adobe AIR. Just authorize the installation, and you're all set. For special circumstances, you can also install Adobe AIR manually.