This is a DC motor with and metal gear with encoder . It is a 6V engine with a 20: 1 metal gearbox and an integrated quadrature encoder that offers a resolution of 11 counts per revolution.

The motor shield is based on the L298 , it is a double complete bridge driver designed to drive inductive loads, such as relays, solenoids, DC and stepper motors. 

Micro Metal Gearmotor 0.9A - 50:1

Motor DC 6V DC 250MA 14500RPM 2,5 ~ 6V DC

50:1 Metal Gearmotor 37Dx70L mm with 64 CPR Encoder

Stepper Motor: Bipolar, 200 Steps/Rev, 20×30mm, 3.9V, 0.6 A/Phase

The 2 Mini Engine Kit (CW+CCW) with Propellers and 4 Axles.

Mini Electric Motor Model for Learning