A Motor Controller is a device that acts as intermediary between your robot’s microcontroller, batteries and motors. A motor controller is necessary because a microcontroller can usually only provide roughly 0.1 Amps of current whereas most actuators (DC motors, DC gear motors, servo motors etc.)

require several Amps. The current a motor consumes is related to the torque it can provide (a small motor will not consume much current, but can’t move a large mass whereas a large motor can move a large mass but will consume a large current).