An IP address is kind of like a physical address.

Maybe your physical address is:

1600 Pennsylvania Avenue
Washington DC 20400

That physical address helps people locate where you live:

• "Washington DC" is the name of the city
• 20400 is the Zip Code in that city
• "Pennsylvania Avenue" is the street in that city
• 1600 is the house number, on that street

So with a couple of numbers and letters, anyone can locate you.  IP Addresses are the virtual equivalent of a locating address.  They are made up of four groups of numbers, like this:

• http://64.233.161.99/

Each set of numbers maps onto some aspect of your location.  It's a bit complicated to explain, but you can read more about it online:

• http://www.google.com/search?q=definition%3A%22ip+address%22

TRACKING SOMEONE DOWN FROM AN IP ADDRESS

IP Addresses are typically tied to the location where you dial onto the Internet.  If you're accessing the Internet from work, or at home on a cable-modem/DSL line... odds are, your IP address is the same over time.  This means if you get someone's IP address, you are one step closer to locating them.

If you are dialing up into the Internet, your IP address will probably shift a bit.  But if you have someone's IP address, then you can usually determine what their ISP provider is.  This is often how police investigators track down hackers on the internet.  They get a subpoena, and with the cooperation of an ISP they track down the user.