x:Key:
Sets a unique user-defined key for each resource in a ResourceDictionary. The key token string is used as the argument for StaticResource markup extension to retrieve any such resource from another XAML usage.
x:Class:
Specifies the CLR namespace and class name for the class that provides code-behind for a XAML page, and names the class that is created or joined by the XAML markup compiler build action in the Windows Phone app model
x:Name:
Specifies a run-time object name for the instance that exists in run-time code after an object element defined in XAML is processed. You use x:Name for element-naming scenarios in the occasional cases where the more convenient FrameworkElement.Name property is not supported.
