Newton gave three laws.
First law -
An object at rest continues to be at rest and an object in motion continues to be in motion till an external force acts on it.
Second law -
The force on an object is directly proportional to the acceleration of the object.
F = ma
Third law -
Every action has an equal and opposite reaction.
Weight = The force acting on a body due to gravity.
Mass = The proportionality constant of the relation force is directly proportional to acceleration.
Gravity = The attractive force exerted by the earth on other objects.