Yesterday, the PR of my website increased from 0 to 2, but the ranking was not improved, so what I want to ask is does the ranking of the website really have no relationship with its PR, what's your opinion?
Google claims PR is just one of 200 factors, and it certainly is the most important. The reliable way to move up in search results is to create good content with good onpage optimization for your keywords.
If you have good content as well as updating regularly will help you to get descent PR. There is no link bet. traffic and PR.
PR is authority, therefore in Google's eyes it means that this website or domain has authority and as bocaj said, there are over 200 factors and PR is one of the important ones but it doesn't always lead to rankings. It also depends on the backlinks coming into your website, how valuable they are etc.
there was a time when PR used to mean higher ranking. for few years now, PR doesn't have much to do with your SERP ranking. it is one of the ranking criteria but doesn't really make any noticeable difference in your ranking. people who chase PR are just wasting their time.