Strange virtual disk. Delete or leave?
The internal virtual disk is a Logical Volume and part of a CoreStorage Logical Volume Group. CoreStorage itself is a logical volume manager similar to Linux' LVM. An LVM is an additional abstraction layer in between hard disks and partitions on one side and volumes on the other side.

In macOS you can convert a partition (e.g disk0s2) with a HFS+ file system lossless to a Logical Volume Group which initially contains several nested items: a Physical Volume, a Logical Volume Family and a Logical Volume. The final Logical Volume is slightly smaller than the original partition, because CoreStorage needs some space to save administrative data.

The Logical Volume contains the data of the previous standard volume/partition and is mapped to its own (virtual) disk device: disk0s2 > disk1
EFI system partition - Usage - macOS:


  On Macintosh computers based on Apple–Intel architecture, the EFI system partition is initially left blank and unused for booting. However, the EFI system partition is used as a staging area for firmware updates.



None should be deleted!