Container -> UIComponent -> FlexSprite -> Sprite -> DisplayObjectContainer -> InteractiveObject -> DisplayObject -> EventDispatcher -> Object

That's pretty scary when you know that it's the main branch without all the other implements, isn't it ? Let's try to know what's the features of each of this inherited classes.

Container -> scrolling, clipping, borders of child components.
UIComponent -> visual components and low-level events like keyboard and mouse input.
FlexSprite -> dumb.
Sprite -> basic display list building block.
DisplayObjectContainer -> if you want to have children and z-order (front-to-back) between them.
InteractiveObject -> interaction from mouse and keyboard.
DisplayObject -> x and y position and transformation matrix of an object.
EventDispatcher -> dispatch events and can be an event target.
Object -> root.