Restoring to new container

[riccardospeggiorin-centropaghe]

I saw the command for restoring in a new container

docker run --rm --tty --interactive -v $BACKUPFILE:/tmp/backupfile.sql.gz postgres:$VERSION /bin/sh -c "zcat /tmp/backupfile.sql.gz | psql --host=$HOSTNAME --port=$PORT --username=$USERNAME --dbname=$DBNAME -W"

Am I getting this right? This create a new fresh container with the postresql dump that I specify? Why I need to specify the $HOSTNAME if is a new container?
thanks

[riccardospeggiorin-centropaghe]

I figured it out.