Neonatal jaundice, or hyperbilirubinemia, is characterized by elevated bilirubin levels in newborns, leading to a yellowish discoloration of the skin and eyes. It occurs in approximately 50-60% of term infants and 80% of preterm infants, with significant jaundice affecting 6% of term babies. Causes include physiological factors, hemolytic diseases, and infections, and management typically involves phototherapy and ensuring adequate hydration.