Domain Name System Zone. A DNS zone is used to host the DNS records for a particular domain. The domain name space of the Internet is organized into a hierarchical layout of subdomains below the DNS root domain.
DNS translates domain names to IP addresses so browsers can load Internet resources. As the number of resource records increases for single domain it becomes complex to manage all of them. A DNS zone refers to a certain portion or administrative space within the global Domain Name System DNS.
Therefore namespace is subdivided into areas zones for this purpose.
The Domain Name System DNS is the phonebook of the Internet. The domain name system DNS is a naming database in which internet domain names are located and translated into internet protocol IP addresses. In most cases you have a 1 to 1 relationship between a Domain and a DNS Zone ie. As the number of resource records increases for single domain it becomes complex to manage all of them.