Newton's Laws consist of three fundamental principles that describe the relationship between motion and forces. The first law, known as the law of inertia, states that an object at rest will remain at rest, and an object in motion will continue moving at a constant velocity unless acted upon by an external force. The second law explains how the velocity of an object changes when it is subjected to an external force. It is often summarized by the equation F = ma, where F is the force applied, m is the mass of the object, and a is the acceleration produced. The third law states that for every action, there is an equal and opposite reaction.