The electrical pulse that keeps us alive is generated by the sinus node (also called the sinoatrial node or SA node) — a tiny cluster of specialized cells in the right atrium of the heart.
Each beat starts there as a spontaneous electrical impulse, which then spreads across the atria, pauses briefly at the AV node, and travels down through the bundle of His and Purkinje fibers to make the ventricles contract. On a heart-monitor trace, this repeating cycle of contraction is what shows up as the pulse.
So in everyday terms: the heartbeat (pulse) is the life-giving electrical rhythm, and its built-in pacemaker is the sinus node.