Do you remember Newton's first law of motion it says "An object is at rest it stays at rest and an object is in motion it will remain in motion with the same speed and direction unless acted upon by an unbalanced force. " Now the question is what happens when the net force acting on the object? That's precisely what the second law of motion discusses. Acceleration depends upon the net force applied, if it is more acceleration will be more if it is less acceleration will be less. The second quantity on which acceleration depends is mass. Acceleration depends inversely on the mass, more the mass, less acceleration, less the mass more acceleration.
The formula of the second law of motion
: F=M×A
DEFINITION: The second law states that the rate of change of momentum of a body over time is directly proportional to the force applied, and occurs in the same direction as the applied force.