Google says the feature is part of its continuing effort to make ads more relevant and useful to users and help advertisers reach the people who are most interested in their products and services.

"AdWords uses a host of targeting and relevancy signals to determine the best ads for each query. However, sometimes a user's query doesn't provide enough information for us to confidently predict what they want," explains Dan Friedman of Google's Inside AdWords Crew. "Take, for example, users who search for "mortgage." Do they want a new home loan or a refinance? Do they want a fixed rate or an adjustable rate loan? Comparison Ads improves the ad experience on by letting users specify exactly what they are looking for and helping them quickly compare relevant offers side by side."

If a user clicks a promotion, they are taken to a page with more detailed, sponsored results. There they can choose from the offers listed on the page or refine their search further. If a user finds an offer they like, they can call the advertiser or request a quote.

"If a user requests a quote, Google automatically anonymizes the user's phone number and sends you a unique code that you can use to contact the user," says Friedman. "You only pay if a user calls the phone number on your offer or fills out a form to request a quote."

Google cites speed, transparency, and privacy as the key points of focus with Comparison ads. They show targeted offers in less than a second, they only show real products (meaning no teaser rates, baits or switch offers), and they won't send advertisers any user information.