Increasing customer traffic :- The banner ad encourages the visitors to go on the advertiser’s website by clicking on it. And through this method, the ad is paid in many ways (CTRs, impressions, time spent on the web page etc.)
Sell a product :- Banner ads encourage you to buy certain products. And here it’s all about the right context and placement. For it to be relevant and effective, the banner ad placed on a certain website has to be related to that niche and to offer an answer to the question the visitor that ended up on that website has.