LVM is a Logical Volume Manager for the Linux operating system.
Logical volume management provides a higher-level view of the disk storage on a computer system than the traditional view of disks and partitions. This gives the system administrator much more flexibility in allocating storage to applications and users.
Storage volumes created under the control of the logical volume manager can be resized and moved around almost at will, although this may need some upgrading of file system tools.
The logical volume manager also allows management of storage volumes in user-defined groups, allowing the system administrator to deal with sensibly named volume groups such as "development" and "sales" rather than physical disk names such as "sda" and "sdb".
Comparison of Linux volume management solutions for Debian users
LVM2 snapshots and udev on Debian
there are some caveats while creating lvm snapshots on debian with udev, see 343671