The atrioventricular node is a specialized cluster of cardiac muscle cells located at the junction between the atria and ventricles that regulates electrical conduction from the atria to the ventricles, ensuring coordinated heartbeats. It is crucial in clinical practice because it controls the timing of ventricular contraction, affecting cardiac output and rhythm stability. Dysfunction of the atrioventricular node can lead to heart block, a condition that may require pacemaker implantation to maintain adequate heart rate.