With Product Search, for example, you can find shopping-related terms, particularly brand names of products that you don't carry, that should be excluded from your campaigns. "When a search query involves a brand name, it's a strong signal that someone is looking to research or purchase a specific item, not check out other brands," Bustos says. "So your general ad will have lower click through, which lowers the click through rate of your entire AdGroup, hurting all your keywords' ad positions and possibly raising your cost-per-click."