Page Authority (PA) and Domain Authority (DA) are both scores developed by Moz that predict how well a specific page or domain will rank on search engine result pages (SERPs).
The main difference between the two is that PA is a score that predicts the ranking potential of a specific page on a website, while DA is a score that predicts the ranking potential of an entire domain (i.e. a website).
Here's an example of a table that shows the PA and DA scores for a few different pages and a domain:

In this example, the homepage, "About Us" page, "Services" page, "Blog" page, and "Contact Us" page all have a PA score of between 45 and 72. The domain (example.com) has a DA score of 85.
As a general rule of thumb, a DA score of 40 or higher is considered good, a score of 50 or higher is considered very good and a score of 60 or higher is considered excellent.
It's important to note that a high DA score does not necessarily guarantee a high search engine ranking for every page on a domain, and a low DA score does not mean a domain will not rank well. Other factors such as relevance, content quality, and the number and quality of inbound links also play a role in determining a domain's and pages' search engine ranking.
Additionally, increasing the DA score of a domain would take more time and effort, as it's based on the overall performance of the website, whereas increasing the PA score of a page could be more targeted and less time-consuming.