ECG stands for Electrocardiogram. It's a medical test that records the electrical activity of the heart over a period of time using electrodes placed on the skin. These electrodes detect the tiny electrical changes on the skin that arise from the heart muscle's electrophysiologic pattern of depolarizing during each heartbeat.

An ECG can provide information about the heart's rhythm, rate, and overall electrical activity. It's commonly used to diagnose various heart conditions, including arrhythmias, heart attacks, and other abnormalities in the heart's structure or function. ECGs are often performed as part of routine check-ups, in emergency situations, before surgeries, or when heart problems are suspected.