Product classes are an extension to the Product Attributes feature that gives a store admin the tools to join products in groups other than product categories and subcategories and filter products in the storefront.
When some products in your catalog have certain characteristics in common and need to be handled together as a group, it may be a good idea to configure a product class for them.
Product classes are listed and managed on the Classes & Attributes page of your store’s Admin area (Catalog > Classes & attributes).
This page allows a store admin to check the number of products with a certain product class assigned and check the list of attributes for each specific product class by clicking the Edit attributes (N) link opposite the product class name.
Product classes will not work without product class attributes configured for them.