A murmur is a sound made by blood flowing through the heart or its valves. It can be heard using a stethoscope during a physical examination. Murmurs are classified as either innocent or abnormal. Innocent murmurs are common in children and usually harmless, while abnormal murmurs may indicate underlying heart conditions. Abnormal murmurs can result from various issues, such as valve defects, congenital heart defects, or anemia. Doctors often use additional tests, like echocardiograms, to determine the cause and significance of an abnormal murmur. Treatment depends on the underlying condition and may involve monitoring or medical intervention.