It can be anything! An apex, subdomain, or even a URL.

Results forb.bna.gr

Resolver

Location

TXT

Name	TTL	Value
b.bna.gr	3600	v=spf1 ip4:65.21.92.197 ip6:2a01:4f9:3b:450c::9 ip4:65.21.92.204 ip6:2a01:4f9:3b:450c::7 ip4:148.251.48.53 ip6:2a01:4f8:202:317::2 ip4:65.108.15.53 ip6:2a01:4f9:6a:4ac9::2 ip4:135.181.178.234 ip6:2a01:4f9:3a:20d5::2 -all