The document discusses the state pattern, including: - Allowing an object to change its behavior based on internal state changes, making it seem like the object is changing classes. - Client code interacts with the context, which behaves differently depending on its current state. - States are often singletons to avoid recreating state instances. - States can access the context via a back pointer or by passing needed data via parameters. - The state can be changed by client code, state instances, or the context itself.