Templates are a bit different than reusable blocks or block patterns. A template is intended to be used in more layout areas. Template (as a term) is for making full-page layouts.
Template Parts
Template parts, on the other hand, are smaller sections of the site that should be decided once and visible in many locations. For example, a header and footer are ideal template parts that can be created completely with WordPress blocks.
When should I use a Template Part?
Template parts are ideal for areas of the site that you don’t plan to modify often, such as the header and footer of your site.