What is an XAML build template?
A TFS XAML build template is a XAML file that contains all the information on how a build should behave when run. XAML looks like XML and is currently, commonly used for WPF, Silverlight, and Universal Applications; where it is used to describe how the UI works, which is different from how it is used in TFS.
Build definitions use build templates. These definitions contain all the metadata, such as selected code paths, build arguments, and any other information that the build template has made available for use by the build definition.