A stork is a large water bird with long legs, a big bill, and a legendary reputation for leaving babies on doorsteps. Real storks don't deliver babies; they mostly stand around in marshes all day.
Myths going back to ancient European folklore describe storks delivering infants to their expectant parents. In Europe, it was considered good luck if a stork made a nest on a house, and that became a handy answer to questions about where babies come from: The stork brought it! Sometimes the common birthmarks on the backs of babies' heads are even called "stork bites."