Also referred to as a banner ad, a banner is a typically rectangular advertisement placed on a website either above, below or on the sides of the website's main content and is linked to the advertiser's own website. In the early days of the Internet, banners were ads with text and graphic images. Today, banners have gotten much more complex and can be ads with text, animated graphics, and sound. Your banners have to comply with Google specifications in terms of dimensions. Animated banners are created in HTML5 format. They are a real attention-grabber for your target and more likely to improve your ads engagement.

More info about Google Ads banner sizes