Domain authority, as determined by Moz, is part of a specific formula. Ultimately, they say that it is a calculated metric that is used to figure out how a domain will rank within the search results of Google. They say that domain authority is based off of data from Mozscape web index. It includes things like MozTrust scores, MozRank and link counts among dozens of other factors. A machine learning model is used in order to predict an algorithm that correlates with ranking across thousands of different search results.
Websites are generally grouped as part of one of three tiers. You have the high authority websites, the mid authority websites and the low authority websites.
Examples of high authority websites include: Huffington Post, CNN, Time, Yahoo, Google, Facebook etc.
Examples of mid authority websites include: community style niche websites similar to SE Roundtable, io9, Gawker, etc.
Examples of low authority websites include: every website that you really haven’t heard of… Too numerous to list.
It’s really important to understand that even though domain authority is very useful, it is not the end of the conversation. It is not the final determining factor that is going to tell you exactly how a website will rank.
There are other things that you have to take into account such as reader engagement, comments, social sharing, networking, syndication and so much more.
At the end of the day, all of these metrics matter when it comes to ranking. But domain authority does play a big role.