Ebb and Flood
Ebb and Flood, sometimes known as Ebb and Flow, is generally an upper tray filled with medium (clay pebbles) and planted directly. However, plants can be contained in separate net pots and placed in the upper tray as well.
The upper tray sits on a larger nutrient tank which holds water, nutrients and a nutrient pump. The upper tray is flooded on a timed basis depending on your plants need - Once or twice a day is usually sufficient.
The nutrient solution slowly drips down to the nutrient tank giving the plant's roots access to oxygen before feeding starts again.
These systems are generally larger and require emptying and refreshing weekly.