Direct drive means the motor transmits the power directly to the shaft of the knife. Here is a diagram explaining the same idea, for a domestic washing machine:
The advantages of direct-drive induction (asynchronous) motor:
Silent operation - low noise during operation.
Maintenance-free - no need to replace belts or motor brushes.
Longer bearing life - minimum axial forces, maximum life.
Compact footprint - takes less space on the kitchen counter!