DNS stands for Domain Name System which is a hierarchical naming system created for translating host names to IP addresses. For example www.google.com translates to 184.108.40.206
A domain name server (or name server) is a computer that houses DNS zones of domain names. This includes A (host) records, CNAME (aliases) records, and MX (mail exchange) records for domain names. Name servers are essentially a piece of the Domain Name System.