No,XAML is not meant only for WPF.XAML is a XML-based language and it had various variants.
WPF XAML is used to describe WPF content, such as WPF objects, controls and documents. In WPF XAML we also have XPS XAML which defines an XML representation of electronic documents.
Silverlight XAML is a subset of WPF XAML meant for Silverlight applications. Silverlight is a cross-platform browser plug-in which helps us to create rich web content with 2-dimensional graphics, animation, and audio and video.
WWF XAML helps us to describe Windows Workflow Foundation content. WWF engine then uses this XAML and invokes workflow accordingly.