The station-based car sharing service assigns a car to each parking space. The rental must end in the same parking lot where it started. This allows you to book in advance the car that you will find at your disposal at the time you choose. Furthermore, you will not have parking problems, because it is reserved for that license plate.
Free-floating is instead the service without parking assignment. The cars cannot be booked in advance, and can be returned within a predefined perimeter.