Who is Ded Moroz?

The kindergarten teacher told the children that in different countries, Ded Moroz is called differently. Anya wondered: who is Ded Moroz really? Grandma believed he was the spirit of winter, grandpa said he was a wizard. Dad insisted he was a kind person, while mom thought he was a postman. But to her younger brother, he seemed like a huge penguin! But Anya couldn't solve this riddle. So she decided to ask Ded Moroz himself…