Heart rate gives you information about how fast your heart beats. The speed can vary as a result of physical activity, emotional responses and certain pathologies. According to the European Society of Cardiology, "a normal heart rate usually averages 60 to 80 beats per minute (b.p.m.)." (source: escardio.org)
A normal heart rhythm originates from the sinus node within the atrium. This electrical stimulus causes the heart ventricles to contract and pump out blood. Some dysfunctions may cause other heart tissues to start an impulse that will disturb the normal electrical sequence. The heart beating out of its normal rhythm is called an “arrhythmia”.