Domain Name System zone(DNS zone)
A segment of the DNS namespace to which administrative authority has been delegated. For example, when sections of the root zone are delegated as top-level domains (TLDs), each TLD becomes an independently administered DNS zone. Likewise, when a TLD divides its namespace into second-level domains, it generally delegates administrative authority to each of those domains, thus creating additional DNS zones.
A parent domain at any level in the DNS hierarchy can optionally delegate administrative authority to any or all its subdomains (children). A zone always starts at a domain boundary and includes a zone file identifies the host servers over which it has administrative authority. A zone ends at the boundary of another independently administered zone.Also Known Aszone