eXtensible Application Markup Language (XAML) allows you to code an applications' presentation aspects separately from the business logic that you code in the PowerBuilder .NET painter Script views.
Changes that you make in a painter Layout view (Design pane) are reflected in the XAML editor code, and changes you make in the XAML editor can be seen in the Design pane. You can view the XAML editor for a painter only when the Design pane is also open, although you can collapse either of these panes and alternately display the XAML editor or the Design pane by selecting the corresponding tab.
There are many Web resources and books available for learning XAML.