A product group is a way to organize the Google Merchant Center product inventory in a Shopping campaign within AdWords. Advertisers can bid on the following product groups: 1) Instead of keywords – shopping campaigns use product groups to determine when items from the Merchant Center account appear on a search results page in a Product Listing Ad. 2) Starting out – when creating a new Shopping campaign, a product group for “All products” is created by default using the default maximum cost-per-click bid set during the ad group creation. 3) Subdividing product groups – you can run your shopping campaign using just the “all products” product group, or subdivide it into as many product groups as you want using product attributes like category, product type, brand condition, item ID, and custom labels. Advertisers can remove product groups as needed. 4) Bidding – is to set and revise bids for each product group as often as needed, or exclude a product group from the campaign 5) Products and filtering – each product can appear in only one biddable product group per ad group. Advertisers can also exclude a product from appearing in a product group entirely by using inventory filters.