Domain Authority is a score (on a 100-point scale) developed by Moz that predicts how well a website will rank on search engines. Use Domain Authority when comparing one site to another or tracking the strength of your website over time. MOZ calculate this metric by combining all of our other link metrics—linking root domains, number of total links, MozRank, MozTrust, etc.—into a single score.
Page Authority is a score (on a 100-point scale) developed by Moz that predicts how well a specific page will rank on search engines. It is based off data from the Mozscape web index and includes link counts, MozRank, MozTrust, and dozens of other factors. It uses a machine learning model to predictively find an algorithm that best correlates with rankings across the thousands of search results that we predict against.
Whereas Page Authority measures the predictive ranking strength of a single page, Domain Authority measures the strength of entire domains or subdomains. The same is true for metrics such as MozRank and MozTrust.