Right now, the experiment seems to be limited to fashion-related queries like [men jackets], [lookbook], [winter outfit], which match videos from YouTube channels like New Look and River Island. "New Look is a South African-owned British global fashion retailer with a chain of high street shops. (...) The chain sells womenswear, menswear, and clothing for teens," according to Wikipedia.
Google only shows labels like: "New Look on YouTube", even though this looks like an experimental ad format. I hope it will never become a regular feature, as it's pretty annoying and it wastes Internet bandwidth.