This excellent tutorial gives an introduction to XAML - the eXtended Application Markup Language.
XAML stands for eXtended Application Markup Language. XAML contain XML that is used to declaratively specify the user interface for Silverlight or WPF applications.
Here are one simple example, if you want to display a circle, given is the XAML code you need to use :
<Grid x:Name="LayoutRoot" Background="White">
<Ellipse Fill="#FF1313D8" HorizontalAlignment="Left" Margin="148,143,0,220" Width="130"/>
When the above xaml is executed, it will display a circle filled with blue color.
You certainly will observe is that XAML is very similar to HTML in nature.