As seen in: https://support.google.com/adwords
The Auction insights reports are different for Search and Shopping campaigns.
The Auction insights report for Search campaigns provides 6 different statistics: impression share, average position, overlap rate, position above rate, top of page rate, and outranking share. You can generate a report for one or more keywords, ad groups, or campaigns (as long as they meet a minimum threshold of activity for the time period selected), and segment results by time and device.
The Auction insights report for Shopping campaigns provides 3 different statistics: impression share, overlap rate, and outranking share. You can generate a report for one or more ad groups or campaigns (as long as they meet a minimum threshold of activity for the time period selected), and segment results by time and device. Auction insights data for Shopping campaigns is available from October 2014 to present.
Descriptions of the Auction insights statistics
Impression share is the number 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. Note that Shopping campaigns don’t use Quality Score. However, overall quality and relevance of your Shopping ads offers do factor into their eligibility. Learn more about tracking impression share.
Overlap rate is how often another participant’s ad received an impression when your ad also received an impression.
For example, if one of the other participants in your Auction insights report is showing “60%” in the Overlap rate column, this means that in 6 out of every 10 times your ad showed, an ad from this participant showed as well.
Position above rate is how often the other participant’s ad was shown in a higher position than yours was, when both of your ads were shown at the same time.
For example, if one of the other advertisers in your Auction insights report is showing “5%” in the Position above rate column, this means that the other participant’s ad showed in a position above yours in 5 out of every 100 times your ads showed at the same time.
This report provides information on other advertisers who participated in the same auctions as you. This doesn’t indicate that the other advertisers have the same advertising settings as you. The other advertisers’ metrics shown are based only on instances when your ads were also estimated to be eligible to appear. This report won’t reveal the actual keywords, quality, bids, or settings from your campaigns, and it won’t give you insight into the same information for others.
While this information is already available by searching on Google—and many already attempt to estimate this data by scanning the ads that appear—this report will make it easier to access and understand this information. It’s available to advertisers whose keywords, product groups, ad groups, and campaigns have a minimum threshold of activity.
Auction insights data is available for Search and Shopping campaigns that meet a minimum threshold of activity. For Search campaigns, you can create a report for keywords, ad groups, and campaigns. For Shopping campaigns, you can create a report for ad groups and campaigns.
- Sign in to your AdWords account.
- Click the Campaigns, Ad Groups, or Keywords tab based on what information you want to see in the report.
- If you’d like to select specific campaigns, ad groups, or keywords, click the box next to each item. Note: you can only select keywords on a single page at a time (unless you run a report for “All”).
- Click the Details box at the top of the statistics table.
- In the drop-down menu, under “Auction insights,” click All or Selected.
- You’ll now be taken to your Auction insights report. Note: only keywords and ad groups that meet a minimum threshold of activity will have the Auction insights report.
- If you selected only Search or only Shopping campaigns or ad groups, you’ll see the corresponding Auction insights report. If you selected a mix of Search and Shopping campaigns or ad groups, you’ll need to select the Search campaigns or Shopping campaigns radio button.
See full explanation here: https://support.google.com/adwords/answer/2579754?hl=en&authuser=1