Flowers are cut from a plant. And with that they are also cut from the veins that via the plants roots and stems supply them with water and nutrition. The organic processes in a flower need, among other things, minerals, glucose and water to make a flower bud for example. But since the flower is cut off of its mother plant it must obtain everything from its vase water. Ordinary tab water does not have the minerals and glucose the flower needs. So if you use the sachet of liquid (for example Vaselife or Chrysal,) you get from the flower shop, you proportionally add the necessary minerals and glucose a flower needs to live.