It’s a new type of ad I was trying. It’s not entirely an ad, it’s mostly a “related pages” feature that sometimes has ads on it. Part of the idea (according to Google) is that by recommending other pages, people spend more time on the site.
As Hex suggested it could be made without the ads but as always that takes time to code and to decide what pages should be related to each other. Google probably knows more about what different pages people visit than I do! Having said that, it often seems quite random in what it recommends. I’m not entirely sold on it but it seems nice enough.
Feel free to comment if you like/hate it :)