Question: What is the difference between WPF and Silverlight?

Is it just the same as winforms vs asp as in desktop apps versus web app or is there an overlap?

Answer: 
WPF is a desktop API that is a replacement to the venerable pixel-based GDI Winforms library. It uses XML layout (XAML) and binding, partial classes and is no longer pixel-based (it deals in units so apps still work where the user has the DPI set differently).

Silverlight is a subset of WPF that runs within a browser, much like Flash.

Silverlight 3 [extended its reach onto the desktop](http://www.infoworld.com/d/developer-world/first-look-microsoft-silverlight-3-challenges-adobe-air-216) as a counter to Adobe Air so there isn't much of a gap between Silverlight and WPF to the point where one has to question the future of WPF. See [Silverlight 3 might kill Windows Presentation Foundation](http://www.sdtimes.com/link/33355).
[One](https://stackoverflow.com/questions/944608/wpf-vs-silverlight) and [two](https://stackoverflow.com/questions/629927/what-is-the-difference-between-wpf-and-silverlight-application).