In the world of SEO, having good and strong back links are vitally important as it helps a website rank better in SERP. It is the most important factor when building your website a foundation as search engines like websites linking to an authoritative domain within your niche. Domain authority tells how your site will perform in search engine rankings. It is also a baseline of how powerful your website is.
It is obviously proven that linking to reputable websites are well ranked and trusted by search engine rather than linking to spammy websites that will only make your website penalize in search engine. However, it is not that simple to find websites with high reputation within your name but it could give your website strong value of links whenever you find some.
Domain authority is measured through inbound links to root domain, inbound links to internal pages and social links popularity. If you have good and quality links pointing to your root domain, it should help increase your domain authority and if you have trusted links pointing to your website pages, it will also add up increase your domain authority.
There are free online tools to know what your website domain authority is and you may analyze how your competitors are performing in search engine rankings based from the results of your domain authority checker. You may use free tools like SeoMoz Open Site Exporer to identify the authority of a domain as well as the authority of each page to know the strength of your domain.
Domain authority is scaling from 0-100 points and the highest is 100 of course. It may be easier for a website to have a score of 20-30 and 30-50 than to 60-80 or 80-100. Obviously, not all websites can earn a score like 80-100 and only Google, Yahoo,Facebook, Twitter and other highly populated websites can earn a score like 80-100.