TCP/IP works like the US Post Office. When you mail a letter the Post Office sorts this letter according to its address, and sends it to its proper destination. Your letter may be transferred to several other Post Offices before it arrives at its final destination.

The computers on the Internet use a similar system. If one computer wants to talk to another computer, it "mails" a message. This message has an electronic address of the destination computer. This message may be transferred to several other "post offices" or routers which determine the best method for the message to be sent. The message finally arrives at the destination computer.