DNS (the Domain Name System)

You want to go to www.wikipedia.org. You type it into your browser. But the browser can't find the website by URL. It needs an IP address, like 185.15.59.224 or 2a02:ec80:300:ed1a::1.

DNS translates URLs to IP addresses by asking name servers:

A DNS iterator asks 'Where's www.wikipedia.org?'. It makes three requests. First to the root nameserver, which tells it the IP address of the org nameserver. Next to the org nameserver which tells it the IP address of the wikipedia.org nameserver. Then to the wikipedia.org nameserver, which tells it the IP address of www.wikipedia.org (Diagram by Lion Kimbro. Public domain. Source.)

Two kinds of DNS lookup: iterative and recursive. This diagram shows iterative. What would a recursive lookup look like?

Try it yourself

nslookup wikipedia.org

What name server did it ask?

You can tell it to use a specific name server, like Google's:

nslookup wikipedia.org 8.8.8.8

Did they give the same or different answers? Try some other URLs.