The Internal Pagerank is the Pagerank computed considering only pages in your analysis scope (pages crawled by Botify), as opposed to the standard pagerank used by search engines which takes into account the entire web - or the part of the web they have visibility over. In other words, the Internal Pagerank indicates how your website's Pagerank is distributed within your website. It shows where your website's link juice flows to: regardless of how much Pagerank your website receives from other websites, you can find out where Pagerank is concentrated on your website, and check if pages your website structure present as important through your internal linking structure (reflected by the Internal Pagerank) are indeed your important pages.
You can see the distribution of Internal Pagerank by depth in the Distribution section of the report:
Internal Pagerank is also of course available in the URL Explorer, through the following fields:
Here are all 3 fields displayed:
If a page has an Internal Page rank which is 1 point higher than another page (9 vs 8 or 6 vs 5 for instance), it means it has roughly 10 times more Internal Pagrank than this other page.