There are three types of disks in VMware. dependent, independent Persistence and non independent persistence. all are utilized under VMware technology. here is some more brief understanding on these types.
dependent disk :- Its a default disk mode and when you take a snapshot of a virtual machine all disks are included in the snapshot under this mode. When you revert back, all data will be reverted back to the previous state.
Independent -Non-Persistent Mode :- Non-persistent mode is read-only virtual disk means When you create any new file, data is not written to a disk. During a power-off process, all data will be vanished or deleted from system.
Independent -Persistent Mode :-Disks in persistent mode behave like dependent disk mode except all data written to a disk stays permanently even you revert back a snapshot. For example you have added a new disk to a virtual machine and you want keep all data permanently even in the event if reverting back the snapshot.