A numeric code that uniquely identifies a particular computer on the Internet. Just as a street address identifies the location of your home or office, every computer or network on the Internet has a unique address, too. Internet addresses are assigned to you by an organization called InterNIC. You register your address with InterNIC as both a name (whitehouse.gov), which is referred to as the domain name, and a number (198.137.240.100), which is generally referred to as the IP address or IP number.

Because the numeric addresses are difficult to understand or remember, most people use names instead like whitehouse.gov or ibm.com. A software database program called Domain Name Service (DNS) tracks the names and translates them into their numerical equivalent so that the computers can understand what they are and find them.

When you have a standard dial-up account with an Internet server provider, you will either be assigned a "permanent" or "static" IP address (i.e. its always the same), or the system will use "dynamic" IP addressing, which assigns you an address every time you log on. If you are an organization and want all of your employees' computers to have Internet access, you can apply to the InterNIC for a range of IP addresses. Most likely, the InterNIC will assign you a Class C address, which consists of 255 unique IP numbers for you to assign to your employees.

If you need more than 255 IP address, you can apply for a Class B address, which will give you over 65,000 unique IP addresses. Class A addresses are for very large companies. Both Class A and Class B addresses are very hard, if not impossible, to get. Usually, companies will get multiple Class C addresses. Actually, we're quickly running out of IP addresses. So the Internet Engineering Task Force, which standardized the IP protocol, is working on a solution.