For you budding programmers, Kirupa has a nice little bit on the principle of inheritance.
For example, if we were to create an Alien class that is based on the Character class, we can say that Alien extends Character. Finally, the word base refers to the class you are extending from. In our examples, the base class is Character since we are extending it to create our more specialized characters.
In ActionScript objects can share the methods of other objects of those methods: triangle and square can walk if triangle can share a little snippet of the “square’s” ability.