Viscosity is indeed the internal friction between fluid layers. It is a property of fluids that determines how resistant they are to flow. When a force is applied to a fluid, such as when stirring a liquid or pushing a piston through a gas, the fluid will resist the motion and exhibit viscosity.

Electromagnetic Force:
Viscosity is caused by the interactions between the molecules or atoms in the fluid. In the case of liquids, these interactions are primarily electromagnetic in nature. The molecules or atoms in the fluid are held together by electromagnetic forces, which can be thought of as tiny magnets attracting or repelling each other. When a fluid is in motion, the molecules or atoms are constantly colliding with each other, resulting in a resistance to flow.

Explanation:
- Viscosity is a property of fluids that determines their resistance to flow.
- It is caused by the interactions between the molecules or atoms in the fluid.
- In liquids, these interactions are primarily electromagnetic in nature.
- The molecules or atoms in the fluid are held together by electromagnetic forces.
- When a fluid is in motion, the molecules or atoms constantly collide with each other.
- These collisions result in a resistance to flow, which is known as viscosity.

Conclusion:
In conclusion, the type of force responsible for viscosity is the electromagnetic force. This force arises from the interactions between the molecules or atoms in the fluid, which are held together by electromagnetic interactions. When the fluid is in motion, these interactions cause the fluid layers to experience internal friction, resulting in viscosity.