Google launched a new ad format for the Google AdSense ad units named full-screen inline ads. Full-screen inline ads are full-screen banner ads that appear inline with your content as a user scrolls the page.
Google said these ads appear below the fold in both Auto ads placements and responsive ad units. There is nothing for AdSense publishers to do to show these, Google said “if you have suitable ad placements, full-screen inline ads will automatically start to appear on your site.”
Here is a GIF of the full-screen inline ads in action:
Forum discussion at WebmasterWorld.