A subdomain is a domain that is subordinate to another domain. Actually, a Second Level Domain (SLD) could be called a subdomain, since it is subordinate to the Top Level Domain
(TLD). In practice, however, the term subdomain is used for domains that are hierarchically below the SLD
domain.Subdomains are therefore also referred to as third level dom
Domain addresses are read from back to front. For example, at www.e-books.itwissen.info, the top level domain (TLD) is *.info, itwissen is the second level domain (SLD), and e-books is the subdomain or third level domain. Other examples of subdomains are"bilder","fotos" or "blog". Subdomains offer large companies the possibility of logical structuring and separation of production operations from sales organizations.