DA (DOMAIN AUTHORITY)is a score [developed by Moz] that hints on the “strength” and relevance of a website for a specific subject area or industry. It's a logarithmic scale of points, typically ranging from zero to 100, which predicts how well a website will rank on search engine result pages (SERPs).
The higher the number of points, the higher is a website's DA.
Now, don't confuse Website’s name authority with page authority. They are different.
While DA tells us about the overall ranking potential of the entire domain or website, page authority (PA) is the ranking potential of a single web page. Both require tools to check.
If you wanted to feature on websites, say maybe to build backlinks, how would you know the most authoritative or reputable ones to target? After all, there are over 1.8 billion websites on the Internet. It turns out there is a rating system! All websites are not rated equal.
Some pack more “respect and reputation” than others. Some are still trying to gain traction. Some have been online for years, steadily building their presence. Some only got registered this year. This disparity that exists among websites gives rise to the need for a rating system, and it's called (DA).