The DNS is the Domain Name System, which makes it possible to associate domain names to groups of Internet ressources and users. More explanation in this video from GoDaddy.
Answer to the following question: how much weight does the number of years a domain is registered for have on your ranking?
Answer to the question by Matt from the Google Webmaster Central. For information, the .co domain name extension is the extension of Colombia.
Matt Cutts from Google answers the question: How would you explain “The Power of Keyword Domains” to someone looking to take a decision what kind of domain to go for?