A name server is the server that houses the network service that translates domain names and IP addresses, mapping numeric (generally) IP addresses into a human-recognizable identifier like a .com domain name. This function is performed by a name server in response to network service protocol requests.
A prime example of a name server’s function is the server element of the DNS (Domain Name System), the most important function of which is the resolution of hostnames and domain names into their corresponding IP (Internet Protocol) addresses.
An authoritative name server is a name server that provides answers to questions asked about names in a zone, and can be either a primary or secondary server. A primary server for a zone is the one that stores all the definitive versions of all records in that zone, while the secondary server for a zone relies on automatic updating mechanisms to maintain a copy of the primary server’s database.
Caching name servers, also referred to as DNS caches, function as a storage container for DNS query results, improving the efficiency and performance of the DNS by reducing the load on authoritative name servers, and root name-servers in particular. Since caching name servers can offer responses more quickly, they also improve the performance of user-end programs and applications that rely on the DNS.