Within the scope of civilian emergency management, a first responder, minimally, is a person with at least basic training in prehospital care, and an assignment that makes them likely to be the first contact of a victim in the field. Such a person may belong to a fire service, emergency medical service, police, or specialized services (e.g., factory safety teams, electrical utility crews).  A related function in the U.S. military is a combat lifesaver, also expected to be the first responder for a prehospital situation, but oriented to minimal essential movement, stabilization and evacuation under combat conditions.
Another aspect of the role is, increasingly, recognizing a terrorism threat, especially from weapons of mass destruction, and sending a specific report to appropriate authorities. In such a situation, the responder may have an even higher responsibility for stabilizing the scene than in caring for individuals.
First responder training is usually on the order of traditional first aid courses, and below the basic emergency medical technician level. This level of proficiency, however, may be a prerequisite for more advanced training.