UWA templates are code conventions for writing clean and meaninful XHTML. Using these will allow you to build powerful user interfaces and make sure your own widget integrate well in the UWA environment.
In order to have the right style or behaviour apply to your widget, those templates provide the proper CSS rules or JavaScript code, along with the expected HTML tree. This way, your widget will perfectly fit with the whole UWA style.
Controls are more elaborate: they offer you powerful JavaScript methods to build HTML components that directly integrate into your widget's design.