I think that was good enough to quote.
"Contrasting Iterative and Recursive Resolution
To help explain the difference between these methods, let's take a side-trip to a real-world case. Suppose you are trying to find the phone number of your old friend Carol, with whom you haven't spoken in years. You call your friend Joe; he doesn't have Carol's number, but he gives you John's number, suggesting you call him. So you dial up John; he doesn't have the information but he knows the number of Carol's best friend, Debbie, and gives that to you. You call Debbie and she gives you Carol's information. This is an example of an iterative process. In contrast, suppose you called Joe and Joe said “I don't know, but I think I know how to find out “. He called John and then Debbie and called you back with the phone number. That would be like recursive resolution.
So in essence, iteration is doing the job yourself, while recursion is “passing the buck”. You might think that everyone would always want to use recursion since it makes “the other guy” do the work. This is true, but “passing the buck” is not considered good form if it is not done with permission. Not all name servers support recursion, especially servers near the top of the hierarchy. Obviously, we don't want to bog down the root name servers and the ones that handle “.COM” and other critical TLDs with doing recursion. It is for this reason that clients must request that name servers perform recursion for them."
From link above.