A Gmail ad shows first in its collapsed form. When someone clicks on the ad, it would either launch an advertiser’s landing page or expand to the size of an email that can be used to meet a variety of advertising goals and can include, for example, embedded forms or video.
People can interact with your expanded ad in different ways, depending on your ad’s layout. They can play video, fill out a form, click to go to your website, or (when they’re on mobile) click to call or to go to an app marketplace.
You aren’t charged when people interact with your expanded ad. You’re only charged once—for the click that expands your ad in the first place.