This shows how a domain’s strongest ad copy evolved over time–and where they use specific variations across their keywords.
The idea is to capture how the whole company message has been tested and improved and which impressions have changed to reflect that. We know that Google will often show the ad that gets the highest clicks. This makes the best performing ad copy rise to the top.
The same information is available when you are searching a term and want to learn which domains have bought ads on it over time. This is usually shown as “Most Successful Advertisers and Their Best Ads.”