In general, a zone is an area of administration. The meaning is similar to that of domain. Specific networking environments use the term to mean somewhat different things:
1) In the domain name system (DNS) environment, a zone is the name space allocated for a particular server. A zone file maintains instructions for resolving specified Internet domain names to the appropriate number form of an Internet Protocol address (an IP address).Content Continues Below
2) In an H.323 multimedia network, a zone is a group of terminals, multipoint control units (MCUs), and gateways within a particular domain. A zone may be a relatively permanent configuration of devices, or just a runtime entity established for a particular event. An administrative tool called a gatekeeper controls interactions for each zone.