Ad Extensions expand your ads with additional information, to be displayed under your ad copy.
By adding more content to your ad, extensions give your ad greater visibility and prominence on the search results page. That means you tend to get more value from your ad. Extensions often increase your total number of clicks, and can give people additional, interactive ways of reaching you.
Extension formats include phone call, so people can call the business directly from the ad, links to other landing pages on the website, and additional promotional text for things like sales or promotions.
Visit the Search Advertising -> Ad Extensions page of your dashboard to add Extensions to your ads.