I've recently been working on product types. The product type layout table allows you to switch different things on and off and to some degree move things around differently depending on product_type being used.

For example you can have show the model number on product_general but turn it off in product_video and those settings are stored in the product type layout table. The key that relates this to your products is the product_type_id. There are other tables which tie the product_type_id to the categories and the products to the categories.

Connie