In Adobe's own words:

"Adobe® AIR® is a cross-operating system runtime that lets developers combine HTML, Ajax, Adobe Flash®, and Adobe Flex® technologies to deploy rich Internet applications (RIAs) on the desktop."

The outcome of this combination of technologies is that developers can design and render quite beautiful user interfaces cross platform. For us desktop Linux users it is nice to have an additional avenue for obtaining and running attractive desktop applications.

Examples of great Adobe air applications are Adobe.com for My Desktop, TweetDeck and the Times Reader. You can download these applications and many more at the Adobe Marketplace.

The easiest way to install Adobe Air on Fedora 12 is to download the latest build from Adobe, click here.

Once you have downloaded the .bin file do the following at the shell:

su -
chmod +x AdobeAIRInstaller.bin
./AdobeAIRInstaller.bin

Once you have Air installed, there is a slight tweak you will have to do to get it running on Fedora 12, it is related to the security certificates. This can be remedied in one simple line at the shell prompt as root.

su -
for c in /etc/opt/Adobe/certificates/crypt/*.0; do aucm -n $(basename $c) -t true; done

What this line is doing is using the aucm which is the Adobe Unix certificate manager to set the certificates installed as trusted.
You will now be able to go to the Adobe Marketplace and download and run Air applications without any issues.

Enjoy!