http://cormachogan.com/2013/04/16/what-are-dependent-independent-disks-persistent-and-non-persisent-modes/

https://communities.vmware.com/message/1982819

• Dependent
  • Disk will be included in VM snapshots
• Independent
  • Disk will not be included in snapshots

• Persistent
  • The disk operates normally except that changes to the disk are permanent even if the virtual machine is reverted to a snapshot.
• Nonpersistent
  • The disk appears to operate normally, but whenever the virtual machine is powered off or reverted to a snapshot, the contents of the disk return to their original state. All later changes are discarded.