Answer: Free fall is the motion of a body under the earth’s gravity alone. It is possible only when no other force (such as air resistance) acts on the body.
When a body falls with only the gravitational force acting on it, its acceleration is g, directed vertically downwards, and this motion is called free fall. The mass of the body does not affect it.
In practice this happens when the air resistance is negligible — for a dense, compact body falling a short distance, or in a vacuum (in a tube from which air has been removed, a feather and a coin fall together).