Adobe has announced it's suite of online apps some time ago, and today the big day is here: Adobe has released Air. What is Air?

Adobe AIR is a cross-operating system runtime that lets developers combine HTML, Ajax, Flash, and Flex to deploy RIAs to the desktop. AIR applications are available virtually anywhere at any time, providing convenient desktop capabilities and working with local or server data. They are developed using modern, efficient programming methods.

So actually, Air provides a mix of local and online data to feed your application. Air is a downloadable client, just like the flash player is. Adobe provides several tools you need to start developing applications here.
Looking at the success of flash applications online, I think Adobe possibly has a very strong position with this release. I think we'll hear more of Adobe Air in the next few months.