Domaining often involves building up of domain name portfolios, or collections of domain names, according to a variety of criteria. Such domain name portfolios often include marketable generic dictionary-word domain names, or domains whose registrations had lapsed yet still retain reasonable traffic. Domain names are the addresses of the web and come in a wide variety of extensions with .com being the most popular in part due to web browsers filling in .com as the default extension when none is given. Although domain reselling may involve a domain used for a website or mail system or else a domainer may generate advertising revenue through domain parking, domaining in essense is not about using the domain names, but keeping them as an investment for the chance of reselling.
CNET has reported that "Today, cybersquatters have rebranded themselves as "domainers."" While an illegal cybersquatter will register names of intellectual property, a domainer will do other things such as automated domain sniping of expired domains, registration of known words, and registering of all domains that are short such as up to four letters.
Some registrars have been accused of domain tasting abuse (see Network Solutions) where once someone searches for a domain's availability in a registrar, if they do not register it right away, the domain is lost and registered by a domainer. While such an action may appear that the registrars are secretly funneling all the names looked up to domainers, this may purely be a domainer's automated system of registering domains that were registered previously and not collusion between a registrar and a domainer and thus only the registrar was involved in domain name front running and not the domainers who bought such domains.
As of December 2006, there are an estimated 8,000 to 10,000 individuals globally who make buying and selling domain names a part of their business. USA Today reported that many Domainers prefer to remain anonymous due to the competitive and controversial nature of their business. In the same report, it was stated that known sales of 5,851 domain names generated $29 million in 2005, compared with known sales of 3,813 names for $15 million in 2004.