1)x:Key is the name of the style
2)TragetType:which control we want to inherit the style
3)Setter Property: we define the attributes where we want to put our style
In following example we are defining style for button and we are giving orange
background for button,italic font style for fonts,
<Window.Resources>
<Style x:Key="myStyle" TargetType="Button">
<Setter Property="Background" Value="Orange" />
<Setter Property="FontStyle" Value="Italic" />
<Setter Property="Padding" Value="8,4" />
<Setter Property="Margin" Value="4" />
</Style>
</Window.Resources>