The VO (Vehicle Order) defines the setup of your car. Like Xenon or LED, Sat, Bluetooth aso.
For some of this VO codes is also a special hardware required (eg. an additional ecu).
But basically VO is also changing the software configuration. If you add a VO code to your car and press the "Code" button on the ECU the system will use the default settings which are behind this VO code to change the software settings.
FDL is hand made change

On this way, you will enter the software configuration by hand and change the settings you would like to have.
Some settings can be changed only by FDL coding because they were never contemplated for the customer.
Hopefully you can understand what I tried to explaine :bigpimp: