Domain: A domain is used to designate a particular location on the internet. Domain names refer to a specific website; however, the term domain also has to do with how these websites are organized on the web.
Common domains include .com, .org, .net, and other designations. For instance, some domains are assigned by country, so they might appear differently. Some top-level domain country codes include .us, .co.uk, .ru, .pl, .se, etc. The United States also has several domains that pertain to organizations and the government, including .gov, .mil, and .edu.
Domain names, on the other hand, are used to distinguish individual websites. Google's domain name would be google.com. Domain names are typically purchased through a hosting company's website. If the registered domain name happens to have a lot of competition, such as if it is a common term, then it may cost a lot. The most expensive domain name on record is Insure.com, which sold for $16 million in 2009.
One way that webmasters may make their domains unique is through a process called a domain hack. The bookmarking website del.icio.us (which is now just delicious.com) is a good example of a domain hack.
In the event that a website contains illegal content, such as pirated materials, then it is possible for the United States Department of Justice to seize a domain. The U.S. government has also passed acts that make it illegal for webmasters to practice cybersquatting, register domain names that are misleading, or redirect users to unwanted websites if a typo is made in the URL (e.g. typing gooogle.com instead of google.com).