1st: any body remains in its state of rest or motion unless acted upon by some external force.
e.g: a ball rolled on the floor continues to roll unless u stop it. it stops because of external force-friction offered by floor, gravitation and air friction
2nd: the rate of change in momentum is directly proportional to applied force and takes the direction in which the force acts.
3rd: every action has an equal and opposite reaction.
e.g: a ball thrown on a wall bounces back due to the opposite and equal force exerted by the wall