Proper way to configure /etc/hosts on Debian 12?

I’m trying to set the hostname and FQDN in /etc/hosts. Do I use the 127.0.0.1 IP or the LAN IP instead?

127.0.0.1 hostname hostname.domain
127.0.0.1 localhost localhost.localdomain

or

192.168.1.6 hostname hostname.domain
127.0.0.1 localhost localhost.localdomain