What is Domain Authority or Domain Rating (DR)?
The Domain Authority or Domain Rating of a website describes its relevance for a specific subject area or industry. The higher a website's Domain Rating (DR), the stronger and more authoritative it is.
Why the "authority" of your domain matters
Google representatives consistently deny the use of "domain authority" as a ranking factor. But according to Google's John Mueller, they do have a sitewide score that "maps to similar things."
Plus, when the correlation between Domain Rating (DR) and keyword rankings was studied for 218,713 domains, it was found that the two correlate well.
So how can you improve your own website's DR score?
When you have high-powered sites linking to your domain it helps Google understand that you are the authority in your niche. It is also a cost-effective way to increase the number of referring domains to your website which is an important ranking factor.