The Engineering Toolbox notes that acceleration due to gravity refers to the constant value of 9.81 meter per second ^2 or 32.174 feet per second ^2. These values are used in physics with Newton's Second Law, which equates the relationship of a force to the product of mass and acceleration.
While any object can be accelerated through applied forces, a free falling object within the earth's gravitational field is subject to this acceleration constant, assuming that friction is negligible. This value is also used for the scientific definition of weight, where it is equal to the product of the gravitational constant and mass. This explains why weights vary in environments with different gravitational fields.