Cardiopulmonary resuscitation
Cardiopulmonary resuscitation (CPR) is a set of actions that should be done if a person stops breathing, or if their heart stops.  The goal of CPR is to force blood and oxygen to keep flowing through the body.  Every part of the body needs blood and oxygen to survive.  CPR does not start a person's heart again.  However, it can keep pushing blood and oxygen around the body long enough that sometimes, it can keep the body from getting damaged by not having enough oxygen.