A zone file is a text file that describes a DNS zone, which is any distinct, contiguous portion of the domain namespace that is managed by a single entity. In most cases, the boundaries of a DNS zone are confined to a single domain; thus, for our purposes only, a DNS zone is the same as a domain.
A zone file is made up of many records. Each record is a mapping between a hostname and a resource. Let's use the DigitalOcean administrative UI to visualize these records and build our zone file.