The approximate 12-month average of user queries for the keyword on Google.com and the Google Search Network.
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The Google Network is a large group of websites and other products, such as email programs and blogs, who have partnered with Google to display AdWords ads.
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The Search Network
AdWords campaigns with keywords are automatically eligible to appear on the Search Network (if this option is selected in AdWords campaign settings). These ads are targeted based on a user's search terms.
т.е. гугл там учитывает не только статсу с гугл.ком, но и статсу с гугл сёрч нетворк, туда входят и обычные сайты с "поиском по сайту от гугла".