Algorithms For Dummies

Explaining the nuts and bolts of PageRank

The innovation brought about by PageRank is that an inverted index of terms isn’t 

enough to determine whether a page matches a user’s information query. Match-

ing words (or meaning, the semantic query match discussed at the end of the 

chapter) between a query and the page text is a prerequisite, but it isn’t sufficient 

because hyperlinks are necessary to assess whether the page offers quality con-

tent and is authoritative.

When discussing sites, distinguishing between inbound and outbound links is 

important, and you shouldn’t consider internal links that connect within the same 

site. The links you see on a page are outbound when they lead to another page on 

another site. The links that bring someone to your page from another page on 

another site are inbound links (backlinks). As the page creator, you use outbound 

links to provide additional information to the page content. You presumably won’t 

use random links on your page (or links pointing to useless or bad content) 

because that would spoil the page quality. As you point to good content using 

links, other page creators use links on their pages to point to your page when your 

page is interesting and of high quality.

It’s a chain of trust. Hyperlinks are like endorsements or recommendations for 

pages. Inbound links show that other page creators trust you, and you share part 

of that trust by adding outbound links on your pages to point to other pages.