Safety includes all aspects of protecting aircraft, passengers and crew from accidents, mistakes and other potentially dangerous situations.
Safety is a very broad topic and includes all measures taken to protect aircraft, passengers and crew from accidents or other incidents. Safety can be achieved and improved in many different ways including aircraft design, airspace layout, crew training, maintenance, flight planning, post-incident investigations and so on.
Note that safety should not be confused with security, which is concerned with protection against deliberate malicious acts.
Use this tag for all questions about how aviation safety is measured, achieved and improved, including questions about accidents and accident investigation. For questions that are purely about security (e.g. anti-hijacking measures) use security instead, although some questions may involve both safety and security.