Is this a universal motor? How does it work?
The motor is most likely a universal motor. A universal motor is DC motor with the armature and field windings connected in series with each other. It can operate with either AC or DC because the armature current is always flowing in the same direction as the field current. Since the same current flows in both coils, the alternating current reverses at the same instant in each coil.

The picture does not show enough detail to allow identification of the yellow thing. There are several possibilities.

If the voltage is increased, the motor speed will increase, but the torque capability will stay the same. That will increase the power because power is speed multiplied by torque. Of course, the driven load will also effect the power delivered.

You should visit some tutorial web sites to get a more detailed explanation. This site is intended for specific questions that have specific answers. Detailed explanations of how things work are difficult to handle in this format.

Safety

If the motor is designed for 110 volts and 220 volts is applied the motor would likely fail quite quickly due to excessive speed, or overheating. It could possibly break apart sending parts flying. Overheating could possibly start a fire. As mentioned in the comment by soosai steven, even running the motor without a load could cause the motor to operate at a dangerously high speed.