Domain Authority (DA) or Page Authority (PA) is a metric given by Moz.com to any website between 1 to 100. It is based off data from the Mozscape web index and includes link counts, MozRank and MozTrust scores, and dozens of other factors. Website with higher DA and PA are likely to appear higher in Google search. Use Domain Authority when comparing one site to another or tracking the “strength” of your website over time.
Whereas Domain Authority measures the predictive ranking strength of entire domains or subdomains, Page Authority measures the strength of individual page.This tool shows the DA and PA of multiple website including number of backlinks.