The breeding sandbox is use to combine two different element dragons, so you will be get information about a new dragon that made from it.
|Dragonvale Breeding Sandbox|
As example for dragonvale breeding sandbox is like if you combine the air with blazing dragon, the result is blazing dragon with time about 8 hours, 15K exp point and 1M dragonvale cash.
The dragonvale breeding sandbox will be helping you to know more about combining the dragon element. You can visit here.