...Once Upon A Time...A young and brave Prince....and a beautiful princess.....yada...yada...yada...
Anyway, he met her just once, and he didn't get anything from her but her address - somewhere in a small country in Europe, in a small town. He didn't know neither the street nor the house (which had a number, of course) - he could only imagine it's on a hill, or in a valley.
He did not know anything about her home or how to get there, BUT, he did know the address... so he decided to write her a letter and ask her out or something....
He put the letter in an envelope, writing his own address on it so she could send her reply. He took the letter to the local post office, put a stamp on it and sent it. Just like that. The workers in the local post office didn't know the destination either, but they did know it is in a foreign country - so they put it with all the other mail that goes to the regional mail office. Since no one at the regional office knew that small country or any postal office there for that matter, they forwarded the mail to the national mail office, where someone knew how to send the mail to Europe, and the letter was forwarded to the small country's central mail office. Over there, everyone knew the county, although not all of them knew the town. Nevertheless, the letter got to the right county, to the right town, and over there - the mail carrier naturally knew the house by its address.
According to the address the prince wrote, the princess could reply in the same manner (only in reverse order of course) .... yada...yada...yada...
....And they lived happily ever after....
This story introduces the way IP Addressing works: you do not need to know where the destination is, or how to get to it, you just need to know the address (the house number stands for host ID - the final destination computer - the rest stands for the subnet and/or net ID. The mail system represents the routers, gateways, and connections on the way...)