Site Explorer (Legacy Reports)
How to use the Internal Backlinks report
In this report, we show internal links to the target domain, subdomain (e.g., blog.domain.com), subfolder (e.g., domain.com/blog/) or URL.

Below are some actionable ways to use this report.
Find nofollowed internal links
Nofollowed internal links block Google from crawling content on your site and prevent the transfer of PageRank.
To find them, enter your domain into Site Explorer and go to the Internal Backlinks report. Add a “Nofollow” filter.

Analyze the report and remove the nofollow attribute on the link where relevant.
See if top-ranking pages are ranking due to internal links
If you see a page ranking well in the organic search results with few or no referring domains, it might be thanks to strong internal links.

To find out, paste the URL of the ranking page into Site Explorer and go to the Internal Backlinks report.

Looks like golfmonthly.com has linked to their list of "best golf club" from a number of internal pages that all have backlinks.
Keep learning
Check out our guide to internal links on the Ahrefs blog: