What is LVM?
LVM stands for Logical Volume Management. It is a system of managing logical volumes, or filesystems, that is much more advanced and flexible than the traditional method of partitioning a disk into one or more segments and formatting that partition with a filesystem. - https://wiki.ubuntu.com/Lvm
WARNING
Below are the steps I took when I replaced my Proxmox 32GB microSD with a 64GB and cloned the installation from the old card to the new one. Do not attempt these steps without first having a backup as there is a high risk of data loss if the partition changes are unsuccessful
Extending a LVM Volume
Further Reading: https://wiki.ubuntu.com/Lvm