Resolv.conf is a computer file used by various operating systems as a DNS resolver. The file is in plain text. It’s usually generated by the system administrator or a network program. The file is located in the /etc/ directory and contains the search domain as well a list of nameservers.
Here’s an example of the /etc/resolv.conf file.
search domain.com local.lan nameserver 18.104.22.168 nameserver 22.214.171.124 nameserver 126.96.36.199
If you have problems resolving domain names, check this file first.