Could you mean the IP address of the DNS server? I think of DNS like a phone book. It’s a list of all the domain names like canadiancancersociety.org and their corresponding IP addresses like 209.15.37.6. the DNS server would basically be “where’s the phone book?” The most common ones being 8.8.8.8 and 1.1.1.1, Google and CloudFlare. I use 9.9.9.9!