For your computer to access domains, you need to have some DNS server set in your network device configuration.
Some people use IPs provided by their ISP, but others use public DNS servers like Google public DNS resolvers 8.8.8.8 and 8.8.4.4

Another alternative is now Cloudflare public DNS service: 1.1.1.1 - https://blog.cloudflare.com/welcome-hidden-resolver/
It seems to be privacy oriented, support DNSSEC encryption and delete ones IP after 24 hours, do not sell data and do not pair data with other CF services you have with them.

Second alternative is http://opennicproject.org