top level domains
second level domains
third level domains
. . .
local domain for the target host
Here is an explanation of the above listing
- root servers
- -root servers are public servers that know about the top level domain servers. Although they are represented by a trailing dot in a URL, the '.' is implied and generally not required.
- top level domains
- -these are the right hand side of the name, such as com or net
- second level domains
- -these often represent an organization, such as example.com
- third level domains
- -third level domains are the first ones that can be a domain or if it is also the left most part it could represents a computer.
- additional levels
- -there can be any number of subdomains depending on an organizations needs.
- local domain
- -this is the most qualified domain that a computer is a member of. It can be any level other than root or top, but is always the second from left most part.
- local host
- -the left most part is usually a computer name, although it could be a domain. Internally, an operating system can be referenced as localhost.localdomain instead of it's formal name.