Google is experimenting with a “Learn more about Sponsored results” label within mobile search ads. The label appears subtly at the bottom right of the ads unit in a light gray style.
The “Learn more” links takes you to: How ads work on Google Search.
This test appears to be tied to Google’s ongoing efforts to make ad disclosures clearer part of the sponsored results redesign introduced earlier.

This update was shared by Brodie Clark and Barry Schwartz.