Rum is made from sugar cane or, more to the point, the ingredients that are a byproduct of sugar cane production, such as sugar cane juice or molasses.
Some craft distillers like to use sugar crystals or dehydrated sugar cane juice due to more convenient storage and the size of their operations. A simple rule to live by is if sugar cane by-product is not used in creating the Spirit, it is not Rum.
Like Whisky, the material ingredient used during fermentation makes up at least half of the flavor profile of the Rum. Depending on the distillery, the fermentation time will differ, ranging from days to weeks at the discretion of the distilling team and what products they are producing.