“Silverlight is a browser plug-in”
In the early days of Silverlight, it was fairly easy to understand that Silverlight content would always be rendered inside of a browser window (whether that be IE, Chrome, Firefox or Safari) where it was surrounded by the hosting HTML content and JavaScript. The HTML was hosting Silverlight rather than the other way around.
Silverlight has a pretty strong interoperability layer between the CLR code running inside the plug-in and the HTML DOM and JavaScript of the surrounding page so you could use Silverlight to exercise some “control” over the hosting HTML/JS and vice versa but HTML was the starting point.
and so if you had a bunch of HTML content to display and wanted to mix in a bit of Silverlight then it was fairly clear what your options were until…
When Silverlight 3 came along, it was possible to take a Silverlight application out of the browser and you ended up with a situation like this;
Read more: Mike Taulty's Blog