How Domain Authority works?

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  Elrey Resultan: May I ask how Domain Authority works? I've read it on moz but I am a bit confused. It is true that the score of your domain authority will determine on what keywords with number of volumes will be use?
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  Jim Munro: Hi +Elrey Resultan ;, thank you for your participation here. :)
  
  DA (Domain Authority) is an attempt by a private corporation (MOZ) to assign a grading number to a site.
  
  It would be calculated from the number and type of links to a site and in turn the DA of the sites linking to that site. That's just my guess BTW I haven't looked into it.
  
  I think it would be useful only when comparing one site's DA to another. I am not an expert but I cannot imagine any case where a DA would be relevant to the keywords a site ranks for.