There are places where it is called volume id like r1soft, while most of the cases they are called uuid. UUID is the unique identifier used in computer system. UUID used in servers, are mostly useful for block devices. To find out the UUID/Volume ID of the block devices run:
blkid
Thin volume shares the same UUID with the thin pool, while solid logical volume would have distinct UUID. To find list of logical volumes, use
dmsetup ls