Letter and Numbers
Imagine you go into a hotel looking for someone who is supposed to be visiting your town. You ask the receptionist if Mr Smith is staying there. The receptionist looks at the records to see if he is there and tells you he isn’t, but suggests there might be a Mr Smith in the next hotel along. You go to the next hotel and ask the receptionist for Mr Smith. This process is repeated until a receptionist you ask finds a Mr Smith in the hotel and sends you to his room.
In this analogy, you are the packet, and the receptionist is the router .
To explain a little more, say you’re surfing the net at www.brighthub.com. To get there, you typed the address into your browser, or clicked a link to it. Your browser knows that to get to Bright Hub it needs the IP address of it. To get anywhere the computer needs to know the IP address of the destination. The names are only for us humans.
Each internet provider has DNS servers, or Domain Name Servers, which are databases of domain names. This database is a massive list of what domain name can be reached by what IP address. These servers compare www.brighthub.com to its list and finds that one is 126.96.36.199.
These lists are constantly refreshed with new information, and if that DNS server doesn’t know what IP address belongs to www.brighthub.com then it will query the massive DNS servers in the internet core which holds all the records for all the websites in that country.