In most Unix-like operating systems and others that implement the BIND Domain Name System (DNS) resolver library, the resolv.conf configuration file contains information that determines the operational parameters of the DNS resolver.
The DNS resolver allows applications running in the operating system to translate human-friendly domain names into the numeric IP addresses that are required for access to resources on the local area network or the Internet.
It also contains a list of IP addresses of nameservers for resolution.
For instance, nameserver 1.1.1.1 configures the resolver to query for the name server with IP 1.1.1.1.
The file is either maintained manually, or when DHCP is used, it is usually updated with the utility resolvconf.