Lets first explain you why the product has been termed as DC Motors? These are basically the means that are very efficient in converting the electrical energy into mechanical energy. The operation of the product is based upon the simple and sorted electro magnetic rule under which the magnetic filed can be created surrounding the current that carries the conductor and allows it to permit to interact with the external laid magnetic field. Post all this take place in the circuit, a rotational movement takes place , making sure about the smooth functioning of the entire process.  Also, termed as shunt motors, DC motors are extensively used where the constant speed is needed and also the starting conditions are noticed to be not very severe.