When a user searches and your ad appears, providing your Google Merchant Center account contains a product that's relevant to the query, product extensions used to appear. These would show images, titles and the prices of your closest matching products just below your ad. When a customer clicked a Product Extension Ad or link, they'll be taken to the landing page listed for that product in your Merchant Center account.
Due to Product Listing Ads becoming the more successful format for advertisers, Google decided to to retire Product Extension ads in late May 2013.
