qcow2 is a virtual disk format.
According to the naming it belongs to vm 101.
What it does? Puh, good question. If you don't know it probably noone does
My approach would be: Make a backup of the pfsense configuration. Shut the VM down. Relocate the file to the desired place. Start VM back up.
The file seems to be active as the timestamp indicates.
So I suspect you just placed it accidentally there.
Vm-102 is your pfsense according to the screenshot.
My approach would be: Make a backup of the pfsense configuration. Shut the VM down. Relocate the file to the desired place. Start VM back up.
Good approach.
Keep in mind that the reallocation can also be done online if you don't want or can to shutdown the VM.
The file format is very likely depending on the storage type underneath.
I have just chosen the "move" option of a Disk and "qcow2" was default format. Once I chose my ZFS pool it switched to RAW.
If you trigger this change via the UI the move operation should just update everything. If you do it manually from the CLI, then it means you need to update the configuration file in /etc/pve/qemu-server
I'd stick with an online move. 10GB is not too large so it will only mean a short interruption for your daily operation. I don't expect this whole process to take longer than 15 mins.