IP Addresses: Names
To make IP addresses readable, a table of names is used to represent
IP numbers. The names are in a hierarchical order; however, there is no one-to-one mapping between name hierarchies and dotted quad number hierarchies.
DNS, or Domain Name Service, provides a name to IP addressing service.
On a Unix machine, one often uses “nslookup” or some similar
program to covert between names and numbers.