The Aura application event propagation framework supports three phases for the propagation of application events: capture, bubble, and default. The capture and bubble phases are similar to DOM handling patterns and provide an opportunity for interested components to interact with an event and potentially control the behavior for subsequent handlers. The default phase preserves the framework's original handling behavior and can be useful for handling application events that affect components in different sub-trees of your app. The emit and control phases are not part of the Aura application event propagation framework. References: Application Event Propagation, Application Events, Communicate with Events