Maybe this is a dumb question, but I can\'t find the answer: in the following xaml what does CommandParameter binding to? Or in general, what does \"{Bind
{Binding ...} is a MarkupExtension.
In its usual form it takes a Path like {Binding Path=someProperty, ...} (or its short form {Binding someProperty, ...}).
So the path in {Binding} is empty which means the Binding is bound to whatever Source there is for the Binding. This might be a little easier to understand if you know, that {Binding} is actually the same as {Binding DataContext,RelativeSource={RelativeSource Self}}.
So in your case CommandParameter gets the value of the current DataContext of the Button.