If you create a Content Type with Post Type selected, it means you can create Posts with it. See Theme Structure to see where Posts go in the Plate Nested layout structure.
Posts have their own url, and are shown in the Content page in the Site Dashboard. they can be created from the sidebar in the Plate Site edit mode.
Post Type theme files have the following paths:
posts/post_type_name/index.plate posts/post_type_name/show.plate posts/post_type_name/other_template.plate