[ Thanks to IdaAshley for this link.
“Logical volume management (LVM) is a way systems can abstract
physical volume management into a higher-level and usually simpler
paradigm. By using LVM, all physical disks and partitions, no
matter what size and how scattered they are, can be abstracted and
viewed as a single storage source. For example, in the layout of
physical-to-logical mapping shown in Figure 1, how could the user
create a filesystem of, say 150GB, since the biggest disk is 80GB
“By aggregating partitions and whole disks into a virtual disk,
LVM can sum small storage spaces into a bigger, consolidated one.
This virtual disk, in LVM terms, is called volume group…”