Yes, it can be confusing at times, but there is a purpose behind the naming conventions for describing the basic functionality of the Stores navigational path.
Departments, sub-departments or categories, themes and templates all relate to the path in which a user might follow to arrive at a product to design in the Online Design Tool. Themes and templates are not used for navigation to Ready to Ship products.
We're going to make use of navigation "breadcrumbs" to help explain the use of these terms. A navigation breadcrumbs or breadcrumb trail is a navigation aid used in user interfaces. It allows users to keep track of their locations within programs or documents. In below example, the breadcrumb is Store Home > Online Design Tool > Banners > Business > Automotive, whereas:
Store Home - starting home page for the Store
Online Design Tool - used to indicate the Design Online Buy Online section of Stores
Banners - department
Business - category
Automotive - theme
Please refer to the screenshots below:
Departments are the top level structure for both Online Design Products and Ready to Ship products. A department is always displayed as a primary (main) navigation link (left navigation on Stores). In the example below, "Banners" "Political Signs", "Printing", "Real Estate Signs" etc are all departments.
Categories or Sub-Departments
Categories or sub-departments are second tier navigation after departments. Often used interchangeably, the primary difference between a sub-department and a category is a theme follows a category (themes and categories go together, whereas a theme is not associated with a sub-department). In the example below, "Business", "Events", Fund Raisers", etc are all categories.
Sub-categories are often used to describe the second tier navigation for ready to ship products. Please see the last section of the article for a screenshot used to help describe a sub-category.
Themes are always associated with a category, and templates are associated with themes. With thousands of template designs available, we must have a way to "categorize" these themes so as not overwhelm the buyer. We do this by creating categories of themes.
Exclusive to the Online Design Tool, a template is a "design idea", made available to the buyer as a "starting point" to aid in their design. As is true in the "real" production world, designs, or templates are built "on" a specific product (including size), such as a 3' x 6' 13oz vinyl banner.
Ah yes, finally, the "end" of the navigational path. A product is a specific item that the user lands on to either design (for Online Design Tool) or to purchase directly (for ready to ship). A product is a specific "item", including size and material specification.
As mentioned above, sub-departments and categories are often used interchangeably. Sub-departments, however, are commonly used to describe the second tier navigation of ready to ship products, such as shown in the screenshot example below. In this example, "Construction Signs", "Regulatory Signs", "Warning Signs", etc, are all sub-departments.