public ICommand HomeViewCommand { get; private set; }

The ICommand interface is the code contract for commands that are written in .NET for Windows Runtime apps. These commands provide the commanding behavior for UI elements such as a Windows Runtime XAML Button and in particular an AppBarButton. If you're defining commands for Windows Runtime apps you use basically the same techniques you'd use for defining commands for a .NET app. Implement the command by defining a class that implements ICommand and specifically implement the Execute method.

XAML for Windows Runtime does not support x:Static, so don't attempt to use the x:Static markup extension if the command is used from Windows Runtime XAML. Also, the Windows Runtime does not have any predefined command libraries, so the XAML syntax shown here doesn't really apply for the case where you're implementing the interface and defining the command for Windows Runtime usage.

check the link for detail

https://msdn.microsoft.com/en-us/library/system.windows.input.icommand(v=vs.110).aspx