Telerik's RadControls are components designed to aid in the development of applications. Telerik offers a whole line of products, from content management systems (Sitefinity) to UI frameworks for web and windows, along with an object-relational mapper tool.  These tools allow developers to create functional, powerful, and stellar web sites.

I say functional in the sense that the user has a rich user interface, leveraging all that AJAX has to offer without having to post back to the server (at least from the server's perspective). I say powerful, because these components give you a lot out of the box that you do not have to recreate. I once was looking to develop an application for a customer that needed some of the functionality that RadControls offered, but without Telerik's framework, I would have spent a lot more hours developing an application that offered them much, much less functionality. Telerik helped me to deliver a better product.

I end with stellar because applications need a better appearance, and Telerik delivers on this by using CSS and images to generate a better UI. It makes use of gradient images for header backgrounds and appealing background images.