hi, may i know what those are for? do i need them if I were to create or use jails?
yes, years ago, but I have never used or need the above when i created or used jails.Have you read ,
https://docs.freebsd.org/en/books/handbook/jails/
# zfs list -r zroot/usr/jail | grep '15.0-'
zroot/usr/jail/15.0-base 557M 1.74T 557M /usr/jail/15.0-base
zroot/usr/jail/15.0-base-jail 518M 1.74T 518M /usr/jail/15.0-base-jail
zroot/usr/jail/15.0-min 130M 1.74T 130M /usr/jail/15.0-min
zroot/usr/jail/15.0-min-jail 88.7M 1.74T 88.7M /usr/jail/15.0-min-jail