Immediate Action
Immediate Actions may be taken on any segment and are not limited to being taken on your turn. Immediate actions occur at the end of the segment, after all other creatures have taken their turn. If more than one creature takes an immediate action in the same segment, then the actions occur at the end of the segment, according to initiative order. Immediate actions may have a recovery time, which adds to your current recovery. Additionally, you are limited to taking only one immediate action per round.
Immediate Actions may alternatively be taken on your character's turn (instead of at the end of the segment). If the Immediate Action has no Recovery Time, then you may take another action directly following the Immediate Action.
Example
Darius is hit with a mighty blow that knocks him off his feet. At the ends of the segment, he uses Quick Stand as an Immediate Action to quickly swing back to his feet.