A name server is a computer server that implements a network service for providing responses to queries against a directory service.
This service is performed by the server in response to a service protocol request.
An example of a name server is the server component of the Domain Name System (DNS), one of the two principal namespaces of the Internet.
It defines the DNS protocol, a detailed specification of the data structures and data communication exchanges used in the DNS, as part of the Internet Protocol Suite.
Historically, other directory services preceding DNS were not scalable to large or global directories as they were originally based on text files, prominently the HOSTS. The Internet maintains two principal namespaces, the domain name hierarchy The Domain Name System maintains the domain name hierarchy and provides translation services between it and the address spaces.
When I change my domain's (a dot com) nameservers it can take up to 2 days. Just curious because my webhosting went down and I have to wait now because I changed nameservers, why?
EDIT: Did some little research and my webhosting says it can MAXIMUM take up to 24 hours.
For my requests they promised responses in 24 hour but missed all the times...
about 5 times in consecutive days until now, no response ever since.
You can use root hints to prepare servers that are authoritative for nonroot zones so that they can discover authoritative servers that manage domains at a higher level or in other subtrees of the DNS domain namespace.