DNS

DNS (Domain Name System) is a hierarchical and decentralized naming system for Internet-connected resources. DNS maintains a list of domain names along with the resources, such as IP addresses, that are associated with them.

The most prominent function of DNS is the translation of human-friendly domain names (such as mozilla.org) to a numeric IP address (such as 192.0.2.172); this process of mapping a domain name to the appropriate IP address is known as a DNS lookup. By contrast, a reverse DNS lookup (rDNS) is used to determine the domain name associated with an IP address.