Complex sentence: Emergency management is the organization and management of resources and responsibilities for dealing with all humanitarian aspects of emergencies--preparedness, response, and recovery--in order to reduce the harmful effects of all hazards, including disasters.
Split into simpler sentences: Emergency management is the organization and management of resources and responsibilities for dealing with all humanitarian aspects of emergencies (preparedness, response, and recovery). The aim is to reduce the harmful effects of all hazards, including disasters.