ColdFusion applications usually use HTML and JavaScript client-side technologies to render their user-interfaces. Since Flex is rendered in the browser and can integrate easily with ColdFusion on the server-side, it is a perfect choice for more dynamic UI interfaces for ColdFusion.
ColdFusion is a server-side language that lets you create dynamic web pages or web services. It is a back-end server technology.
You use ColdFusion to generate HTML programmatically before it is sent by the web server to a requesting client browser.
ColdFusion is also used to process form data sent from a client browser.
The web server passes the HTTP request to ColdFusion when you request a URL. All program state is lost between requests without special programming.
A web application written in ColdFusion consists of .cfm (or .cfml) and .cfc files on the host server, which are created by a developer with an IDE (such as Dreamweaver, CFEclipse, or HomeSite) or a text editor.
ColdFusion can talk directly to a database server such as MySQL, Oracle, or SQL Server.
Because ColdFusion creates HTML, intimate knowledge of HTML coding is also required for professional results.
Implementing event-driven user-interfaces and animation effects requires use of JavaScript and HTML.
How does it compare to Flex?
With ColdFusion, both application logic and layout execute on the server, which returns HTML to the browser. With Flex, a SWF file embedded in the web page executes on the client machine.
The GUI of a ColdFusion application is generated HTML and optionally supporting JavaScript.
All the advantages and limitations of HTML-based design apply to a ColdFusion-based application. Flex is generally not limited by HTML layout constraints.
ColdFusion can talk directly with a database server, and therefore can be used to write web services. Flex does not communicate with the database directly; however, it can consume data from a web service and display it.