The modern misconception from most people is that plants require soil to grow, however, it is the nutrients contained in the soil that the plants need to help them grow.
There are several ways to grow plants using hydroponics including NFT, Flood and Drain, Drip Irrigation, Aeroponics, Passive.
With Gravity Fed Hydroponics, pots are filled with soil or coco that are situated above a tray of water that is filled with nutrients. This tray of water is connected to another tray or reservoir. Nutrients are sent from the water tray and into the coco or soil. The pots are separated from the water tray by a nutrient feeder tray.
Using a Gravity Fed Hydroponics system the plants are fed regularly and at the right time without the danger of waterlogging the growing material as they are never left to sit in water.