Parabolic Motion
Parabolic motion is a term that describes the motion of the footbag through the air. Often the bag is described only as moving up and down, which is just for the sake of simplicity.
[. . .]
Parabolic motion as applied to footbag freestyle is essentially simply the natural gravitational effect of setting the footbag up with a certain amount of force and at a certain angle (which affects the width of the parabola) which determines the height and ultimate landing place of the footbag.
Footbag Worldwide Wiki - Parabolic Motion - by Steve Goldberg