An IP is a four byte address representing a network node (ie. a computer or network) under the internet protocol (hence the name, IP). IPs are used for locating other nodes on a network to establish a communication link. Without an address, it would be very hard to find a node. Each byte can have a value in the half-open range [0..256), so there are plenty of unique IPs to go around (though with the explosive growth of the internet, a new IP protocol has been devised called IPv6).

What do you mean your friend has a useful IP? Is he trying to hack a system or something?