It’s the Moz’s probability of prediction about the authentication of particular page that would be ranked in Search Engine Result Pages(SERPs), as mentioned earlier that score starts from 1 to 100. Page Authority can be greater than Domain Authority depending upon the worth of that particular page and flow of traffic. Collection of data from MozScape Web Index which includes link counts, Moz Trust and Moz Rank is processed through machine learning model that actually defines best correlation of such pages with thousands of SERPs.
Page score usually starts from 1 and ends at 100, it is easy to gain score up to 30 and quite hard to move beyond 80 due to lot of competition and other factors.
What is a Good Page:
Determining factors that may affect the authenticity and genuineness of a particular page based on the comparative metric which also has more powerful influence in SERPs comparatively.
Page Authority Vs Domain Authority:
Methodology used in calculation of PA and DA is quite similar but there is a slighter difference here, you may say that Page Authority is the strength and authenticity of single page while Domain Authority defines the strength of whole domain and sub domains.
Tools to find Page Authority:
Different types of tools are used to check the page authority of single website, most of them are free so you may easily access these websites to check PA of any website and page. Smallseotools, Open Site Explorer, MozBar and Keyword Explorer will give you an opportunity to search PA for free.
How to improve Page Authority:
Like Domain Authority, parameters for Page Authority are same, these matrices defines the credibility of single page, the more you link your page on different High Domain Authority websites, the more chances you get to improve your Page Authority.
Crux of the Topic:
Having almost same meaning and matrices used to calculate Domain Authority and Page Authority Nevertheless the difference remains same and may cause a big reason to make your posts Google friendly, i would suggest you to improve your PA while improving your DA. Hope this information would help you a lot.