I want to understand PV

I learning k8s and I have a little problem to understand PV.

For example, I want to deploy PostgreSQL which store data in /var/lib/postgresql/data
I want to use my local disk for PV so I created that and set my path: /mnt/ssd/Kubernetes/Postgres
I do not understand how PV and PVC will store my data, because I created pod1 with PostgreSQL, created new DB and kill this pod1. New pod2 still have database which I created few second time ago on pod1 but on my local disk in /mnt/ssd/Kubernetes/Postgres I do not have any files, so

  1. How new pod2 know about created database? How PV store data about my created database?
  2. Why does PV need my disk if it doesn’t hold any data on it?