Pediatric surgery is a subspecialty of general surgery that deals with the diagnosis and treatment of surgical conditions in children. The conditions could be congenital (present from birth) or acquired ( develop after birth).
Common congenital anomalies in children are:

Inguinal hernia
Hydrocele
Undescended testis
Umbilical hernia
Different types of cyst, sinus and fistula
Intestinal structural anomalies
Cleft lip and palate