By far the most common way to build Windows Phone applications is to use XAML and C# (or VB). In this case the XAML is a variant on Silverlight, which made it very easy for developers building Silverlight applications to switch across to building Windows Phone applications. 4 years on and the number of Silverlight developers has dropped (well at least the appeal of being a Silverlight developer has), and all the focus now is on becoming a Windows developer. Unfortunately somewhere along the lines the Windows team decided that having three XAML frameworks (WPF, Silverlight and WP) wasn’t enough and that they needed to come up with another, only marginally different, framework. This we’ll refer to as Windows XAML.