Templates are "convinience" components designed to speed the process of creating new composite components. Each template provides a "pattern" for some common function that the devleoper "drops" into a component, remanes as required and then fills in the missing template parts and/or adds prots, sub-components and properties as required.
For each template there will be "Template Slots" documentation. Template slots indicates what elements must be filled in for the template to work. In add ition to these, the developer is free to add other elements as may be required.