Core Commerce provides a messaging system that lets you configure multiple message types. You can then send the messages to slots used by an application (see the Personalization Programming Guide), or send them as JMS messages to be used by scenarios. Out of the box, this system is used by Gift with Purchase promotions (see Gift with Purchase Promotions in this guide) and by the stacking rules feature (see the Merchandising Guide for Business Users). You can extend the provided framework for your custom components.