White cranberry juice is the juice of the cranberry (Vaccinium oxycoccos), a low growing shrub native to the cooler parts of the northern hemisphere, including the United States.
White cranberries are simply mature cranberries that are picked before they've had time to change color from white to red. White cranberry juice is less acidic, less bitter, and sweeter than regular cranberry juice, and can be used in cocktails when a lack of color is desired.