Domain Names
Domain names are often referred to simply as domains.
Domain name registrants are frequently referred to as domain owners, although domain names, technically, are leased from a registrar.
Every domain name ends in a top-level domain (TLD) name, which is always either one of a small list of generic names (three or more characters), or a two-character territory code based on ISO-3166 (there are few exceptions and new codes are integrated case by case).
Some of the more recognizable TLD's are: .biz, .com, .edu, .gov, .info, .mil, .name, .net, .org, and .us.
In addition to the top-level, or root, domains, there are second-level domain (SLD) names. These are the names directly to the left of .com, .net, and the other top-level domains. As an example, in the domain en.wikipedia.org, wikipedia is the second-level domain.
Next are third-level domains, which are shown immediately to the left of a second-level domain. In the en.wikipedia.org example, en is a third-level domain. There can be fourth- and fifth-level domains, and so on, with virtually no limitation. An example of a working domain with five levels is www.sos.state.oh.us. Each level is separated by a dot, or period symbol.
Domains of third or higher levels are also known as subdomains, though this term technically applies to a domain of any level because even a top-level domain is a "subdomain" of the "root" domain (a "zeroth-level" domain that is designated by a dot alone).
Traditionally, the second-level domain has been chosen based on the name of a company (e.g., microsoft.com), product or service (e.g., gmail.com). The third level was commonly used to designate a particular host server. Therefore, ftp.wikipedia.org might be an FTP server, www.wikipedia.org would be a World Wide Web server, and mail.wikipedia.org could be an email server. Modern technology allows multiple servers to serve a single subdomain, or multiple protocols or domains to be served by a single computer. Therefore, subdomains may or may not serve any real purpose.
Domain names are often referred to simply as domains.
Domain name registrants are frequently referred to as domain owners, although domain names, technically, are leased from a registrar.
Every domain name ends in a top-level domain (TLD) name, which is always either one of a small list of generic names (three or more characters), or a two-character territory code based on ISO-3166 (there are few exceptions and new codes are integrated case by case).
Some of the more recognizable TLD's are: .biz, .com, .edu, .gov, .info, .mil, .name, .net, .org, and .us.
In addition to the top-level, or root, domains, there are second-level domain (SLD) names. These are the names directly to the left of .com, .net, and the other top-level domains. As an example, in the domain en.wikipedia.org, wikipedia is the second-level domain.
Next are third-level domains, which are shown immediately to the left of a second-level domain. In the en.wikipedia.org example, en is a third-level domain. There can be fourth- and fifth-level domains, and so on, with virtually no limitation. An example of a working domain with five levels is www.sos.state.oh.us. Each level is separated by a dot, or period symbol.
Domains of third or higher levels are also known as subdomains, though this term technically applies to a domain of any level because even a top-level domain is a "subdomain" of the "root" domain (a "zeroth-level" domain that is designated by a dot alone).
Traditionally, the second-level domain has been chosen based on the name of a company (e.g., microsoft.com), product or service (e.g., gmail.com). The third level was commonly used to designate a particular host server. Therefore, ftp.wikipedia.org might be an FTP server, www.wikipedia.org would be a World Wide Web server, and mail.wikipedia.org could be an email server. Modern technology allows multiple servers to serve a single subdomain, or multiple protocols or domains to be served by a single computer. Therefore, subdomains may or may not serve any real purpose.