A banner ad can link to a “Landing Page” and/or go to a website URL.
A landing page is essentially a full page ad for your sponsor. When the user clicks on the banner ad they can be taken to the landing page which can show the sponsor’s information, etc. It is built into the app rather than a URL, where it would take them to a specific website.
If you would like to have both a landing page and a URL, after clicking on the banner ad, the user will be taken to the landing page. They can then click on the landing page and be taken to the website for the URL that you have provided.