Google Webmaster Tools - Internal links
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See below for screenshot and explanation of Internal links which is within the Your site on the web category.
Here are the Google webmaster tools categories as they look when you are logged in (left).
Webmaster tools - Your site on the web - Internal links
Internal links highlight how the internal link structure of your website is performing. Google likes the webpages within a website to link to each other in a logical pattern with important pages or high level category pages being linked to the most.
See the Google tools Help page on "Internal Links" (new window).
Here is what the Internal links category looks like in Webmaster tools (screenshot below) using my website's data as an example.
Screenshots on this page are copyright © 2016 Google Inc.
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