Since IP addresses are rather difficult to remember (and are not particularly descriptive), the Internet also allows you to specify a computer by a name rather than a number string. For example, the machine at MIT with the IP address 18.72.0.3 can also be referred to as: bitsy.mit.edu.
This whole string is known as the computer's host name. In this string, the first part ("bitsy") is the name of the machine itself, while everything else ("mit.edu") is the domain name.
The domain name is the name of a network associated with an organization. For sites in the United States, domain names typically take the form: org-name.org-type