Newton's laws of motion, foundational principles in classical physics, encapsulate the relationship between a body and the forces acting upon it, along with its motion in response to those forces. There are three laws: the first law describes inertia; objects remain at constant velocity unless acted on by an external force. The second law quantifies force as the product of mass, acceleration, and changes in momentum over time. The third law states that for every action, there is an equal and opposite reaction, indicating the reciprocal nature of forces.