The common way a DNS server is configured to handle requests. The DNS server makes multiple requests to the various DNS servers on the Internet in order to wind up with the actual IP address of the website requested. If the DNS server is not set up as recursive, then each request made to a DNS server would go back to the client machine, which has to issue the next request until the IP address of the desired site is retrieved. See DNS
In this example, the client machine makes one query to the ISP's recursive DNS server. If the server were not recursive, the user's machine would have to query the DNS server, the .com server and the authoritative server to obtain the IP address of ABC.COM.