A user gets an ip address of 192.168.0.1 from the company network administrator. a friend of the user at a different company gets the same ip address on another pc. how can two pcs use the same ip address and still reach the internet, send and receive email, and search the web?

Both computers are seen as having the same IP address externally. Your router will relay requests to the originating computer and the procedure used for this is Network address translation. However, if you were to try to communicating with your father's computer, you would use your internal addresses