Flourite is a plant substrate. It will hold nutrients for your plants to utilize better than sand will which will help them grow root systems faster.
I actually just switched from flourite to a dirted tank capped with sand. I did that because I really hated the flourite because of how it looked. It just made my tank look dingy.
In either case you don't actually need a plant substrate to have a successful planted tank, it just helps. In either case you will need root tabs.