Visual Studio Documentation Page o' the Day: How to Locate and Organize Project and Item Templates

Template files must be placed in a location that Visual Studio recognizes in order for the templates to appear in the New Project and Add New Item dialog boxes. You can create custom subcategories for templates so that these subcategories appear in the user interface.

For details, see https://msdn.microsoft.com/en-us/library/y3kkate1.aspx.