ColdFusion is an application server that runs on a web server. It runs on Linux, Solaris, Windows servers and even the personal web server on Windows 98. The ColdFusion Web application server works with the HTTP server to process requests for web pages. Whenever a Cold Fusion page is requested, the ColdFusion Application Server executes the script or program the page contains. Unlike JavaScript and Java applets, which run on the client, ColdFusion runs on the Web Server itself. Scripts you write in Cold Fusion will run the same way on every browser. You build applications by combining standard HTML with a straightforward server-side markup language, the Cold Fusion Markup Language (CFML).

As with other server-side scripting languages, ColdFusion offers the ability to interact with data and the user, thus transforming your website from simply a collection of static pages into a living site that can interact with either the browser or a database. The advantage of using ColdFusion above other scripts is that such interaction is seamless; CFML can be incorporated alongside HTML.

ColdFusion is the better choice if you are short on development time and it lends itself well to the novice programmer; it is also good for sites with large databases. However ASP pages can be easily transformed into other scripting languages whereas ColdFusion's distinct code makes it rather inflexible.

The primary feature of ColdFusion is its associated scripting language, ColdFusion Markup Language (CFML), which compares to JSP, C#, or PHP and resembles HTML in syntax. "ColdFusion" is often used synonymously with "CFML", but it should be noted that there are additional CFML application servers besides ColdFusion, and that ColdFusion supports programming languages other than CFML, such as server-side Actionscript.

Originally a product of Allaire, in 2001 the company was purchased by Macromedia, who subsequently merged with Adobe Systems in 2005.

ColdFusion is most often used for data-driven web sites or intranets. More advanced users can use ColdFusion as a productivity layer above a J2EE platform or use ColdFusion as middleware in a service oriented architecture (SOA), generating SOAP or RESTful web services or Flash remoting.

ColdFusion can also handle asynchronous events such as SMS and instant messaging via its gateway interface, available in ColdFusion MX 7 Enterprise Edition.