What are the important (most common) features of Silverlight 4.0

I am working on reading up on Silverlight 4 and wanted to know what are the most commonly used functions of Silverlight (so I can put a stronger empha开发者_运维百科sis on them) as opposed to features that are rarely used.

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Here you can find five great features of silverlight 4.0.

Short preview:

1. Webcam and Microphone
2. WebBrowser & HTMLBrush
3. Full Trust in Out of browser
4. Printing
5. RichText edit