Domains provide identification of the website on the Internet and define it in space. They can consist of several levels or parts. The domain name exists thanks to the special DNS system. The address is formed in a form, convenient for the person, and facilitates storing of the characters necessary for transition to a certain website. On the basis of domains on the Internet the whole business which is based on sale of the easiest for storing and input of names for higher price is constructed.
The full domain name can consist of a body and all sub-names which it enters. These names are separated by points and form levels. For example, ru.sait.com designates the resource of the third ru level entering the second sait level which enters space of the top order of com.
At conversion of a domain name the system of the DNS servers is used, each of which holds one or several zones and responds to the corresponding requests. All levels are available only after registration procedure which is made by loggers to provide protection of the rights of the owner. The information about the person who registered a name is brought in a certain DB and is public. For identification of the busy domain it is possible to use whois service.
The beautiful addresses of the websites are on sale at the different price in numerous zones. Over time it becomes harder and harder to pick up a good name therefore the resale market appeared. It included the companies registrars, hostings and the different organizations which buy and sell domains and are engaged in advertizing. About 30% of the websites have no information, and exist only for purchase and sale of advertizing links. The domains consisting no more than of three digits, letters or names which are in consonance with the most widespread nouns of English in singular have the greatest commercial value.
Also there is a concept of national domains which are selected for a certain country and have designations from two letters. Currently there are about 260 geographical names. There are also internationalized domains which contain characters of alphabets of any given country. Also there are special backed-up names which are used as examples for documentation and testing.