Newton's Law refers to the three fundamental principles of motion formulated by Sir Isaac Newton in the 17th century. These laws describe how objects behave when forces act upon them. The first law states that an object at rest stays at rest, and an object in motion continues in motion unless acted upon by an external force. The second law explains that the acceleration of an object depends on the mass of the object and the amount of force applied, summarized by the equation F=ma, where F is force, m is mass, and a is acceleration. The third law states that for every action, there is an equal and opposite reaction.