In the early days of Google, PageRank was a very important piece of information about a website. It let you know the general authority level of a site and how well it would tend to rank against similar content on another site. The PageRank toolbar, released in 2000, became an important tool in the SEO world.
Over time, Google de-emphasized PageRank, partly because people were gaming the system and partly because they switched to emphasizing other factors when ranking a site. They eventually stopped updating PageRank data and in 2016, they finally shut off the toolbar.
There have been other metrics created, such as Domain Authority by Moz, but nothing has quite been a proper replacement.
Now that the PageRank patent has expired, companies are free to implement their own versions. Domcop has done just that, using the Common Crawl data to calculate PageRank for the top 10 million domains on the web.
You can use it here: https://www.domcop.com/openpagerank/
As of the time of this post, Xangis.com has an OpenPageRank of 3.40.