During normal event processing, action methods and action listener methods are fired during the "invoke application" phase of request processing. If this attribute is set to "true", these methods are fired instead at the end of the "apply request values" phase.

If the value is an expression, it is expected to be a method binding EL expression that identifies an action method. An action method accepts no parameters and has a String return value, called the action outcome, that identifies the next view displayed. The phase that this event is fired in can be controlled via the immediate attribute.

If the value is a string literal, it is treated as a navigation outcome for the current view. This is functionally equivalent to a reference to an action method that returns the string literal.