What's in a Name: Addresses and IP Numbers
The only detailed information one needs when dealing with the Internet is the address of Internet members. Each institution attached to the Internet receives a unique domain name and can then in turn assign addresses to members of its network to identify them uniquely to the Internet. There are some guidelines and application processes to follow when obtaining a domain name that are handled by a local system administrator. Usually, the domain name and the subsequent local names of network stations reflect something about an individual participant of the Internet. For example, Dartmouth College has the domain name dartmouth.edu, and a particular station on the Dartmouth College network is called dartvax.dartmouth.edu, or carr.dartmouth.edu. Each station on a network also has a unique four-part numerical address in addition to its name, called the IP number. For example, the IP number of dartvax.dartmouth.edu is 22.214.171.124. The first two parts of that number reflect the domain name and are the same for all stations of the Dartmouth College network. The last two parts of the number can be assigned by Dartmouth College to the individual stations on its network.
When you need to address a particular station on the Internet, you could use the name of that station ( dartvax.dartmouth.edu) or the corresponding IP number (126.96.36.199). Usually, the station name is the more convenient address to use, and it is automatically converted to an IP number by a name server behind the scenes. In some cases, however, you may want to refer to a station directly by its IP number.
Knowing the name of a station usually reveals something about its origins. For example, addresses ending in '.edu' refer to educational institutions in the US, '.com' to commercial institutions in the US, '.org' to non-profit organizations, '.de' to German Internet members, and so on.
In many cases, the first part of an address tells you also about the service that will be provided by the machine behind the address. For example:
Bert G. Wachsmut