Short answers, pulled from the story.
Newton's laws of motion are three physical laws describing the relationship between the motion of an object and the forces acting on it. The first law states a body stays at rest or in uniform straight-line motion unless acted on by a force. The second law states net force equals mass times acceleration, or the rate of change of momentum, and the third law states that two bodies exert equal and opposite forces on each other.
Isaac Newton first stated the three laws of motion in his Philosophiae Naturalis Principia Mathematica, published in 1687. He probably settled on the Principia's presentation of three primary laws during 1685, having arrived at the set incrementally from a 1684 manuscript that listed four laws.
Newton's third law states that to every action there is always an equal and opposite reaction, meaning the mutual actions of two bodies upon each other are equal and directed to contrary parts. For a book resting on a table, the Earth's gravity pulls the book down, and the reaction to that action is the book's own gravitational pull on the Earth, not the table's support force.
All bodies fall with the same acceleration regardless of mass because combining Newton's second law with his law of universal gravitation makes the falling body's mass cancel from both sides of the equation. In free fall near the Earth without air resistance, speed grows in proportion to elapsed time and distance falls in proportion to the square of elapsed time.
Newton's laws break down in extreme cases, prompting new theories such as quantum mechanics and relativity. Special relativity modifies the definition of momentum and the third law because simultaneity is relative, general relativity reimagines gravity as curvature of spacetime, and quantum mechanics connects to the second law only inexactly through the Ehrenfest theorem.
Aristotle divided motion into natural and violent and claimed air pushed a javelin forward after it left the hand. John Philoponus, a sixth-century Byzantine Greek thinker, rejected this and proposed impetus, a quality carried within a moving body that was a forerunner of momentum, while Galileo developed the modern concept of inertia in Two New Sciences in 1638.