[Jon Stratis]

You always want to have some sort of gearing between your motors and what they're driving. For a drive train, this almost always means a gear box of some sort. This helps to reduce the wear on your motors (because the shafts aren't placed under the strain that the shafts for the wheels or arms are placed under), making them last longer. Further, it allows you to chose how much torque/speed you want by changing the size of the gear reduction.