The Stopped Falling behavior will "watch" a selected object and trigger an event as soon as the selected object has stopped falling.
A stopped falling state means the selected object suddenly changes the vertical velocity to zero, Unless it is a Joystick Controlled object. Joystick Controlled objects are only put into a stopped falling state if their velocity is zero and they collide with the ground.
This is the object that will trigger the event when it stops falling. By default the current object is selected, but you can tap the graphic and choose any other object in your scene.
This outputs the Object ID.
If you wanted to a parachute to close when your object lands.