DWC (Deep Water Culture) units are commonly referred to as "bubblers" and are used for a method of growing plants hydroponically in a bucket of nutrients with the plant suspended over the nutrients and the roots growing down into the nutrients which are super oxygen saturated by pumping large volumes into the nutrient solution with the aid of an aquaurium stlye pump with an airstone attached to the airline.
Plants grown in this method grow at superfast rates due to the fact that they are being fed large amounts of oxygen. This is the same reason that the roots can sit in the nutrient solution without drowning. This method of growing is perfect for a hobby grower or one who wishes to grow for personal use. Large scale commercial growers do not generally find this method appropriate for the reason that each plant is housed in its own reservoir, and would simply be entirely too much maintenance in a large scale grow.
For someone who only needs say 6 plants, this method of hydroponic cultivation is an excellent way to grow. When an environment has been created to provide your plants with the optimum conditions required for fast, healthy growth,the one limiting factor left is how much oxygen can be provided to the roots of the plants. DWC growing will take care of this factor and then some! The roots will recieve huge amounts of oxygen for some of the fastest growth rates possible. DWC is one of the easiest and yet most effective forms of hydroponic cultivation.