Interpolates between its begin and end values.
Just defines how to interpolate between two values.
Many types have specific Tween subclasses that provide type-specific interpolation.
You can define your own interpolations by creating your own subclass of Tween and overriding its lerp function.
Combine a tween with an animation
To get a concrete value for the current frame of an animation, you also need an animation to determine the current state.