DNS is a system that helps connect ease-of-use features and services (think, email) with the underlying plumbing of the internet. DNS for your domain can usually be set up through your domain registrar.
DNS is an acronym for domain name system.
For example, DNS lets you type google.com into your browser, and have the correct page display. Under the google.com is navigated to through its IP address. Its IP address is
188.8.131.52. This is more difficult to remember than google.com. DNS translates your request to see google.com into a request to see.
Read more about DNS: https://www.cloudflare.com/en-ca/learning/dns/what-is-dns/