“Debriefing” is a widely used term with many different meanings. On the other hand, Critical Incident Stress Debriefing (CISD) is a specific term used to describe a small group process designed to assist individuals who have been exposed to unusual, stress-provoking, and potentially traumatic events, including natural disasters, accidents, and violence.
During a CISD, participants have an event-focused facilitated conversation sometimes described as a structured small group story-telling experience. You will be asked to discuss the event from your perspective and to share your thoughts and feelings about it.
The group leader, usually a counseling professional, guides the process and provides information about reactions to trauma, signals of distress, and practical coping methods.
This is not counseling or psychotherapy and is certainly not a substitute for therapy.
Rather it is a supportive, focused discussion of the traumatic event. Such small group “psychological first aid” is designed to allow group members to reflect on the impact of the event, normalize reactions to it and to assist and promote recovery.
For more detailed information see:
http://www.webmd.com/mental-health/critical-incident-stress-debriefing
http://www.info-trauma.org/flash/media-e/mitchellCriticalIncidentStressDebriefing.pdf
http://www.aaets.org/article54.htm