This is the old Russian folk tale. "Sivka-Burka" means chestnut and grey and this is traditional appellation of any horse in the tales.
An old peasant had three sons. The two older brothers were smart, but the youngest was a fool named Ivanushka. One day the peasant discovered something was trampling his wheat field at night. The older brothers each stood watch but fell asleep. But Ivanushka caught the thief - a wonderful chestnut-gray stallion with a gold saddle and silver bridle.
The horse told Ivanushka that if he let him go he would help fulfill his wishes. He said, "When you need me, come to the field, whistle, and call 'Sivka-Burka, come!'" Ivanushka agreed and let the horse go free.
One day the tsar organized a competition. He placed his daughter in a high tower on the twelve pillars and announced that if someone on horseback could jump high enough to take the ring from her finger, he could marry the princess. While his brothers were gone to the competition, Ivan called Sivka Burka, Ivan climbs in one ear and out of the other he turns into a handsome prince. They galloped off to the tsar's courtyard.
After three tries in three days Ivan reached the princess and took the ring from her finger. But he galloped off so quickly that nobody saw his face. At home he turned back into the fool Ivanushka and bandaged one hand, telling his brothers that he had injured himself.
Next day there was a big feast at the tsar's palace. Everyone in the land was invited, and Ivanushka's whole family went. At the end of the feast the princess served everyone honey. She saw the bandage on Ivanushka's hand and ordered him to untie it. He opened his hand and there was her ring for all to see. With the help of Sivka Burka Ivanushka turned into the handsome man again and married the beautiful Princess.
