Domain names are formed by the rules and procedures of the Domain Name System (DNS). Any name registered in the DNS is a domain name. Domain names are organized in subordinate levels (subdomains) of the DNS root domain, which is nameless. The first-level set of domain names are the top-level domains (TLDs), including the generic top-level domains (gTLDs), such as the prominent domains com, info, net, edu, and org, and the country code top-level domains (ccTLDs). Below these top-level domains in the DNS hierarchy are the second-level and third-level domain names that are typically open for reservation by end-users who wish to connect local area networks to the Internet, create other publicly accessible Internet resources or run web sites.
In 2009, Bluehost introduced a new feature called CPU throttling. CPU throttling (at Bluehost and similar hosting services) refers to the process of reducing user's CPU usage in whenever the particular user is pulling "too much" server resources at one time. At that particular time, Bluehost would freeze (or drastically reduce) client sites' CPU usage substantially. This effectively shut down clients' websites hosted on the Bluehost server for several hours throughout the day.