I hope you are referring to Newton's Laws of Motion by "Newton's Law".
There are three laws quoted by the great physicist of all time Sir Isaac Newton.
These laws are the building-blocks of the field of the Physics known as Classical Physics or Classical Mechanics.
Law 1. If no force applied externally, then a body in rest will always be in rest and a body in motion will continue to move in a straight line with a uniform velocity.
Law 2. The rate of change of momentum is directly proportional to the force applied and the direction of motion is always in the direction of the force applied.
Law 3. Every action has an equal and opposite reaction.
The Law 1 is also called the law of Inertia.
From the 2nd law, we can derive the equation of force, that is F =m.a (m = mass; a = acceleration)