cycloidal reducers are used to minimize power size

cycloidal reducers are used to minimize power size and total machine size and handle heavy shock loads. This term is often used interchangeably with gear drives, mechanisms used to provide a variable output speed from a constant speed power source or to increase torque for a variable speed power source.
single stage gearbox are similar and are referred to as gear heads when they are mounted directly onto a motor instead of just a shaft.