Silverlight is Microsoft's competitor to Adobe Flash. You may see a lot of flash content in web sites these days. But Silverlight is still fairly new, and if you haven't come across web sites that use Silverlight exclusively to enhance the web pages, then you don't need it.
It's possible that you will need it at some time in the future if it's use increases across the web. Also, it is effectively just a browser plugin, so it doesn't take up much disk space. So if you do install it then it just sits there, waiting to be used if needed.
I am using internet explorer 8 on my home laptop, with windows xp pro.
I have heard there is a prog called Silverlight, which one can download and install, but am wondering: what is the advantage of using this program. Do i need it on my system, which seems to work alright at the moment without Silverlight.
Yours with thanks