In magration, animal travels in other places or it means they travel to other places where the weather is warmer or they can find food so they can live.
In hibernation, That is necessary because in winter many mammals wouldn't find food and
if they wouldn't hibernate they would starve to death. Hibernation works
by eating up what you could call an energy pack made of fats. One could
say the fat also "protects" them from the ice cold winter.