You might like a product to appear in more than on product group in the product catalogue.
The products "main" product group and product type are displayed in "Manage Product".
Using "Additional Product Groups" , the product can here be linked to be appear in more than one product group.
E.g. SKU CODE: PH123 - Phillips Small Screw Driver
Might have "Tools" as main Type and "Screw Drivers" as main Group.
Using Additional Product Group you can also link this product to appear in a Type called "Sale" and a product Group called "Garage Specials" .
Seel also: Manage Catalogue, Type of Goods and Groups.