Silverlight 3

->Can SilverLight run in other platforms other than window?
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.

->What is the relationship between Silver Light, WPF and XAML?
XAML is a XML file which defines the UI elements. This XML file can be read by WPF framework or Silver light framework for rendering. Microsoft first developed WPF and they used XAML files to describe the UI elements to the WPF framework. Microsoft then extended WPF and made WPF/e which helped to render the UI in the browser. WPF/e was the code name for Silver Light. Later Microsoft launched Silver Light officially.
So the XAML just defines the XML structure to represent the UI elements. Both the frameworks i.e. WPF and Silverlight then reads the UI elements and renders the UI elements in the respective platform.

->Even WPF runs under browser why SilverLight?
Yes there is something called as WPF browser application which can run WPF in browser. For WPF browser application you need .Net framework to be installed in the client location while for silver light you need only the plug-in. So in other words WPF browser applications are OS dependent while SilverLight is not. SilverLight plug-in can run in other OS other than windows while we all know .NET framework only runs in windows.

->What is the difference between Silverlight 1 and Silverlight 2
Nothing, Silverlight 2 is a full superset of Silverlight 1.0 - it is 100% compatible with Silverlight 1.0 applications and provides significantly more powerful features and functionality. Silverlight 1.0 applications even benefit from improvements in media playback and performance characteristics of Silverlight 2 with no additional work.

->What kind of audio video formats are supported in Silverlight?
Silverlight supports Windows Media Audio and Video (WMA, WMV7-9) and VC-1, as well as MP3 audio.

->What is Silverlight Tool Kit?
To create an application or game you need to design, code and give some extra feature to your output.
To do the above, you need some controls, IDE etc.
Silverlight Tool kit is nothing but is a collection of Silverlight Tools, Components etc. It includes source code describing the all you need to develop an application.
The Silverlight Toolkit is a collection of Silverlight controls, components and utilities made available outside the normal Silverlight release cycle. A product of the Microsoft Silverlight product team, the Silverlight Toolkit adds new functionality quickly for designers and developers, and provides the community an efficient way to help shape product development by contributing ideas and bug reports. It includes full open source code, unit tests, samples and documentation for over 26 new controls covering charting, styling, layout, and user input.

->Can I add more than one .xaml pages in silverlight application?
Yes, you can have multiple .xaml files in a single project.In the App.xaml, in the method Application_Startup you can choose, which page you want to initially display.