Hi Sapna,

Instead of explaining here i suggest you to go through the below link,

http://www.learn-silverlight-tutorial.com/WhatIsSilverlight.cfm#h1.3

Silver light is a web browser plug-in by which we can enable animations, graphics and audio video. You can compare silver light with flash. We can view animations with flash and it’s installed as a plug-in in the browser.

Yes, animations made in SilverLight can run in other platforms other than window. In whatever platform you want run you just need the SilverLight plug-in.