Cardiopulmonary resuscitation (CPR) is a lifesaving technique used in emergencies when someone's heartbeat or breathing has stopped. It involves a combination of chest compressions and rescue breaths to maintain blood flow and oxygenation to vital organs until professional medical help arrives. CPR can be performed by bystanders and is crucial in cases of cardiac arrest or drowning. The procedure typically starts with calling for emergency assistance, followed by chest compressions at a rate of 100 to 120 compressions per minute. If trained, the rescuer can also provide rescue breaths. Early CPR can significantly increase the chances of survival and recovery for the affected individual.