Heart defects refer to problems in the structure or function of the heart that are present at birth. These defects can affect the walls of the heart, the valves, or the blood vessels near the heart. Some common types of congenital heart defects include atrial septal defects, ventricular septal defects, patent ductus arteriosus, and coarctation of the aorta. These conditions can range from mild to severe, with some requiring surgical intervention or other treatments.