This section runs down some of the terms you'll encounter in the rest of the internals documentation.

• A State is an object that's used to control the order of API function calls. There are currently four State classes: AnyOrder, Command, Error, and Sequence.

• Containers are a subclass of States. A Container is a State that can contain other States. There are currenly two Container types: AnyOrder and Sequence.

  Since Containers contain States, and since all Containers are States, Containers classes may contains instances of themselves and each other.