Consider you type the URL www.techcuriosity.com on your browser, what happened behind the scenes to get you this page? All communication on internet is through IP address. So when you access a site from your browser, the plain text "domain name" has to be converted to an IP address. The browser contacts a DNS server for the IP address. The DNS server will start searching for the IP and contacts the ROOT DNS server. There are root servers for all top-level domains [ .COM, .INFO, .NET, .ORG, .GOV ] etc which keeps a record of all the IP address. Your name server will then contact the .COM DNS server and request for the IP address of www.techcuriosity.com. The .COM DNS server will not know the IP address of www.techcuriosity.com but it will know the IP address of the name server that handle the domain www.techcuriosity.com, so it returns that IP address. Your name server then contacts the DNS server for www.techcuriosity.com and request for the IP address of www.techcuriosity.com. The DNS server will return the IP address of www.techcuriosity.com to your browser. Then your browser contacts the server for www.techcuriosity.com. Thus your browser serve's you the requested page. All the DNS server's keep a record of the recently visted websites. This is know as caching. Once the DNS server resolves a request, it caches the IP address it receives. Caching speeds up the request, since it already know the IP of the requested domain and there is no need to repeat all the above process to resolve. There are multiple sets of DNS servers at every level, so if any of them fails other's will resolve the request. This help you to find the website at point of time and makes the internet redundant.
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