Motion tweens are applied to symbol instances and text fields. Only symbol instances and text fields can be tweened; all other object types are automatically wrapped in a symbol when a tween is applied to them. The symbol instance can contain nested symbols, which can themselves be tweened on their own timelines.

The minimal building block in a tween layer is a tween span. A tween span in a tween layer can contain only one symbol instance. The symbol instance is called the target instance of the tween span.

Only one symbol can be used at a time in a motion tween. If you add a second symbol to a tween span, Flash replaces the original symbol in the tween. You can change the target object of a tween by dragging a different symbol from the Library onto the tween span in the Timeline. You can delete the symbol from a tween layer without removing or breaking the tween. This allows you to add a different symbol instance to the tween at a later time. You can also change the type of the target symbol (button, graphic, or movie clip) of a tween span.

You can edit individual property keyframes on Stage, in the Property inspector, or in the Motion Editor.

A tween layer can contain tween spans as well as static frames and ActionScript. However, frames of a tween layer in a tween span cannot contain objects other than the tweened object. To add additional objects in the same frame, place them on separate layers.

When a tween contains motion, a motion path appears on the Stage. The motion path shows the position of the tweened object in each frame.

Apply easing to motion tweens to vary the rate in which the animation moves; if no ease setting is applied, the animation moves at a consistent rate on each frame throughout the tween.