The Domain Name System (DNS) is a decentralized naming system for Internet resources such as websites, mail servers, and other resources that use the Internet Protocol (IP). It translates domain names, which are easy for humans to remember, into IP addresses, which are numerical labels that are assigned to every device connected to the Internet.
In essence, the DNS acts like a giant phone book that maps domain names to IP addresses. When a user types a domain name into their web browser, the browser queries the DNS servers to resolve the domain name into an IP address. The DNS then returns the IP address to the browser, which then uses the IP address to request the website's content from the corresponding web server.
Here are a few resources for further information about the DNS:
DNS basics: https://en.wikipedia.org/wiki/Domain_Name_System#DNS_resolution_process
How the DNS works: https://howdns.works/
ICANN (Internet Corporation for Assigned Names and Numbers), the organization that oversees the DNS: https://www.icann.org/resources/pages/dns-sec-2013-09-19-en
DNS performance and security: https://www.dnsperf.com/
I hope this information helps!