XAML, its purpose in wpf is to create user interfaces which  arranges the position of buttons, panels and controls etc. the designers and the developers can work together effectively on a same project because of it.

1. An application has an App.xaml:

 

  1. <Application x:Class="WpfApplication1.App" 
  2.              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
  3.              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
  4.              StartupUri="Welcome.xaml"> 
  5.     <Application.Resources> 
  6.           
  7.     </Application.Resources> 
  8. </Application> 

 The StartupUri defines the first window to be opened, <Application.Resources>tag defines