What are the two types of brushless servo?

Brushless DC motor and DC motor are two concepts. Although the name of the brushless DC motor is DC, it is actually not a DC motor. From a classification point of view, DC motors are one category, while DC brushless motors are synchronous motors. In short: DC servo motors specifically refer to DC brushed motors, and DC brushed motors and DC brushless servo motors cannot be collectively referred to as DC servo motors.