Cardiopulmonary resuscitation (CPR) is a life-saving technique used to maintain oxygenation and circulation during cardiac arrest, with effective implementation improving survival rates. The procedure includes chest compressions and artificial ventilation, performed immediately on anyone who is unconscious and pulseless, while contraindications include do-not-resuscitate orders. Key principles involve restoring circulation and preventing brain damage, with specific steps outlined for both lay rescuers and healthcare providers.