Larry Page, Google and PageRank
PageRank is a Google Algorithm that assesses the SEO authority that domains have earned in links from other domains, often called “Domain Authority”. It is the first iteration of how Google ranked pages based on inbound links. This is published in Google’s first patent discovery document and is public knowledge and always has been. The PageRank of a page in this iteration is calculated by adding the page rank of every page that links to it (except for links from the page itself) and dividing it by the number of outbound links on that page, reduced by the damping factor, to 1 minus the damping factor.
What is tbPR? (Toolbar PageRank)
Google used to publish a representation on a scale of 1-10 known as toolbar PageRank (tbPR) via a browser plugin that should a pipe chart with the scale of PR of a page/domain name and also made it available via an API. This somewhat backfield as people became obsessed with it and it led to a widescale rise in link buying.
What is PageRank and Domain Authority
Since Google yanked its practice of publicly sharing PageRank, some 3rd party OEM SEO Tool providers, like SEMrush, Moz, and AHrefs have built their external version, often called “Domain Authority” or “DA” for short. While it represents some kind of scale of authority between domains, its biggest shortcoming is not being able to tell if domains or pages on those are demoted or dont pass good authority, undermining the whole interlinked DA chain and rendering it often useless but dangerous especially when buying domains.
What is Domain PageRank?
Domain PageRank is the PageRank of a domain. PageRank is still the fundamental backbone of SEO according to the Google SEO Starter Guide.
Keyword Difficulty and Domain Authority
KD%’s are based on the domains that rank and their Domain Authority.
Backlink Gate and PageRank
By the time Google realized this that people were buying backlinks faster than gas, it was too late – resulting in the suspension of a large number of domains that were targeted by the Google Search Quality team and algorithmic updates. Google subsequently pulled the tbPR browser plug-in and API – which was also used by SEO tools like WebCEO and Alexa (a former search engine turned SEO tool) which has since been replaced by a public version called Domain Authority, which has been subject to much debate and a lot of skepticism in the SEO community.
Link Spam
Link Spam is the process of acquiring or buying backlinks to boost authority in Google rankings and manipulate PageRank/Google search and strongly violates the Google Web Search Policy Guide. Unfortunately, Link Spam is often confused with Toxic Backlinks but it is unrelated and often just FUD or fear among SEOs, especially of Negative SEO attacks, a rarity in reality.
See also: What is the Google CrUX (Chrome User Experience) Report?