Cardiopulmonary resuscitation, usually called CPR, is an emergency lifesaving technique used when someone's heart stops beating or they stop breathing. The word itself tells you what it does: cardio means heart, pulmonary means lungs, and resuscitation means bringing someone back to consciousness.

When someone performs CPR, they push hard and fast on the center of the person's chest to manually pump blood through the body, keeping oxygen flowing to the brain and vital organs. They may also give rescue breaths to put air into the person's lungs. This helps keep the person alive until professional medical help arrives with equipment that can try to restart the heart.

You've probably seen CPR performed in movies or TV shows, though real CPR looks less dramatic and more exhausting. It requires serious physical effort to push deep enough and fast enough (about 100-120 compressions per minute, roughly the beat of the song “Stayin' Alive”).

Learning CPR is something many people do through training classes offered by organizations like the Red Cross. While it's not appropriate for kids to practice on real people without proper training, understanding what CPR is helps you know what to do in an emergency: get adult help immediately and call 911 or your local emergency number. Knowing CPR has helped countless ordinary people save lives when someone collapsed from a heart attack, drowning, or another medical crisis.