XAML : XAML is another schema that derives from XML that describe content presentation for parsers that render WPF and Silverlight windows phone. The XAML schema can be further defined to parse WPF or to parse for Silverlight.
HTML: HTML has a defined schema with tags that describe content presentation for a web browser or anything that uses HTTP and parses HTML. HTML isn't exactly XML that would be XHTML but it's gotten better.
XML: is data storage that can exchange with most technology cross plate form.
