Both a SEO term and an algorithm created by Google for ranking pages.
While your pages official PageRank score can no longer be obtained, as Google retired the official testing tool in 2016, most SEO tools like Ahrefs, Semrush and many more, create their own version of PageRank, usually in an effort to attribute a weighted value of authority to a website or domain.
PageRank, the algorithm, appears to still be in use to this day, likely still using inbound and outbound links, and the PageRank of those pages, to weigh and rank pages across the internet.
Note: If you would like to read the original 1997 paper on the algorithm, written by Google founders Sergey Brin and Larry Page, you can find it on Stanford University's website: The Anatomy of a Large-Scale Hypertextual Web Search Engine.