What Flex Is. (Score 5, Informative)

For those asking: At a real basic level, Flex is an XML language that let's you compile Flash applications. Developing an application in Flash directly is extremely time consuming, and not suited for developer types.

On a more complex level, Flash based Flex applications are robust interactive SOA applications with the ability to easily hook into various data services (JMS/Messaging, AMF[POJOs,OpenAMF via PHP, Coldfusion CFCs], XML over HTTP, and WebServices/SOAP).

So you can make rich desktop like applications with all the great stuff like drag and drop, interact with video, webcams, microphones, key events like CTRL and Function keys. Thin clients, where the app loads once. But have the deployment ease of a web application, and are platform agnostic (unix,mac,windows,pdas,cellphones,etc....).

Though the best way to see what it's all about is to look at live applications on the web:

http://maps.yahoo.com/beta/Yahoo Maps
http://www.thoughtfaqtory.com/flex/mxnaviewer/main .swfBlog Reader
http://weblogs.macromedia.com/pent/flickr/PhotoSea rch.htmlFlickr PhotoSearch.