Vehicle Identification number or more commonly a chassis number, in order to perform more complex functions, you will be required to store a VIN number to proceed.
VCDS will always ask beforehand, so depending on what you are trying to do, you can make the decision then.

This is the maximum number of vehicles you can work on with full functionality, as previously mentioned when you need store a VIN it will be permanently embedded and cannot be deleted, each of the kits can be upgraded to its next level, this is done directly with Ross-tech on their website at an extra cost.

You will only be able to use basic functions of VCDS on any other vehicle, other than the ones stored – operations like scanning, fault finding and clearing codes, anything that requires entering a control module will not be possible. You will need to purchase an upgrade from Ross-Tech to work on more vehicles, which is handy if you do not wish to spend a lot initially and do not mind upgrading your lead during the many years you use it.

All kits perform eXactly the same full functionality, the only difference is the VIN storage limitation and the ability to use the full functions with vehicles – Unlimited kit has no storage limitation, so is naturally the most expensive.