Templates and their associated themes provide the layout and styling for pages and widgets. Sitefinity CMS templates use the ASP.NET master page pattern for WebForms-based templates and layout files for MVC-based templates.
Feather supports use of MVC controllers on Web Forms pages and hosting of Web Forms and MVC controllers on the same page. Page templates can support Web Forms, MVC, or both. If you create a new template, you will specify whether you plan to use Web Forms, MVC, or a hybrid of the two.
ASP.NET MVC or Web Forms outlines some of the pros and cons of each approach.
The following documentation links provide information about creating and modifying templates and themes:
Template overview