You think of this web site as k12irc.org. Your computer or phone thinks of it as 165.140.71.129. How a web site name is converted to an Internet address is the job of DNS. DNS also provides information like where to send emails (MX records), how to confirm that email is not spam (DKIM, SPF, DMARC), ownership information (SOA), which DNS servers are authoritative for the domain (NS) and more.
This post shows how this all works and the 7 step process it takes to get you from domain name to computer address. The “the recursive DNS servers” are the local servers provided by your Internet Service Provider (and sometimes by your own WiFi router).