What is SilverLight?

Hi,
I want to know what is SilverLight?
I am using Internet Explorer & want to know why it prompts me to install SilverLight on my PC?

Hi,
What is Silverlight?

Silverlight is a new cross-browser, cross-platform implementation of the .NET Framework for building and delivering the next generation of media experiences and Rich Interactive Applications(RIA) for the web. It runs in all popular browsers, including Microsoft Internet Explorer, Mozilla Firefox, Apple Safari, Opera. The plugin required to run Silverlight is very small in size hence gets installed very quickly.

Silverlight aims to compete with Adobe Flash and the presentation components of Ajax. It also competes with Sun Microsystems' JavaFX, which was launched a few days after Silverlight.

A programming model for developing and distributing rich Internet applications (RIA) that use graphics, animations or video within the .NET framework. Silverlight was previously known by its code name, Windows Presentation Foundation Everywhere.

A plug-in from Microsoft for delivering media created with Silverlight. The Silverlight plug-in is both cross-browser and cross-platform. Notably, this makes it interoperable with Apple's OS X and both the Safari and Firefox Web browsers, along with Windows and Internet Explorer. Microsoft's decision to create a plug-in for all three major Web browsers is both an acknowledgement that it does not control the browser market and a strategic push drive adoption by both the development community and installation by consumers of online media.

Thanks guys,
should have mentioned I had read MS sights, I was just trying to
understand better.
It does appear to be a enhanced method of video/audio presentation, a MS flash type setup.

From what I can tell it's basically Microsoft's equivalent of Flash.

To install the plug-in takes practically 5 seconds, and it's done (less time
that installing Flash Player, that's for sure).