Think of AIR as a container to create and run mini applications in their own private windows, combining Flash, HTML, Javascript, and other so-called Web 2.0 tools. Like Java but without the power. Bascially, Adobe is creating their own private little space on your desktop.
Adobe AIR is a cross-operating system runtime that allows web application developers to use their existing web development skills (HTML, Javascript, Adobe Flash, Adobe Flex, Ajax) to build and deploy rich Internet applications on the desktop.
9WR – Adobe AIR: Multimedia capable, cross-platform desktop environment to develop mini-applications.