Each computer on the Internet has an IP address that uniquely specifies it worldwide. You can think of an IP address as analogous to a postal address. When you dial into an ISP, the ISP's gateway assigns your computer an address (like a post-office box) that stays the same for the duration of your connection. When you log off, the ISP can assign the same address to another user. An IP address looks something like 192.80.94.133; this happens to be the IP address of the Holy Cross Math/CS Department's web server. If you have a permanent Internet connection, you have a ``static IP address'' (like a street address).