The report contains the following fields:
- Average position
Average position is a quick way to gauge how high your ads are ranking compared with those of other advertisers competing in the same auctions. Average position is the average rank of the ad in the auctions, which determines the order of the ads on the search results page.
- Impression share
Impression share is the percentage of impressions you received divided by the estimated number of impressions you were eligible to receive. Eligibility is based on your current ads' targeting settings, approval statuses, bids, and Quality Scores. In the Auction insights report, impression share also tells you the impression share of other advertisers as a proportion of the auctions in which you were also competing.
- Overlap rate
Overlap rate tells you how often you and another advertiser received impressions at the same time for this keyword.
- Position above rate
Position above rate tells you how often another participant's ad was shown in a higher position that yours was in auctions in which you both received impressions.
- Top of page rate
This statistic tells you how often your ad (or the ad of another advertiser, depending on which row you are viewing) was shown at the top of the page, above the organic search results.
Here is a screen shot that you can enlarge:
You can access it on the keyword level by clicking on the icon on the left of the keyword and then on the "activity report" option:
For more details, see this help page.
Forum discussion at WebmasterWorld.