Tech/Protocols/DNS/DNS Zone

A zone is a portion of all domain name space. So .com is a portion of domain name space and thus a zone.

Zone file

A Zone file is a non-vendor specific way of describing a zone.

Example being a Zone file for example.com

$TTL    3600
@       IN      SOA     example.com. email.example.com ( 1 1w 1d 2419200 1w )
@       IN      NS      ns.
@       IN      A       203.0.113.10
@       IN      AAAA    2001:DB8::5
; 203.0.113.0/24 rfc5737
; 2001:DB8::/32 rfc3849

Zone files are also used to map IP addresses to names. Here is an example for the zone

113.0.203.in-addr.arpa

$TTL    1h
113.0.203.IN-ADDR.ARPA.         IN      SOA     ns.example.com. email.example.com. ( 1 1w 1d 1w 1h )
        IN      NS      ns.example.com.
10       IN      PTR     www.example.com. 
2       IN      PTR     ns.example.com.
3       IN      PTR     mail.example.com.

More info at https://en.wikipedia.org/wiki/Zone_file