Every actor has a basic set of motions that it can use to perform the actions to achieve a goal. But to interact with objects, it is the object itself that offers the motions to the actor. Such a set of motions is stored seperately so that different objects with similar interaction possibilities can share them.
An actor has a dedicated “motion container” in which the motions specific to the object it is interacting with are loaded. Every time a new object is chosen, new motions are loaded into this container, thus unloading the previous ones and keeping memory usage low (and the actor stupid 😉 ).