The word, Hydroponic, comes from Latin and means working water. Simply put, it is the art of growing plants without soil.
The science of soil-less gardening is called hydroponics. It basically involves growing healthy plants without the use of a traditional soil medium by using a nutrient like a mineral rich water solution instead. A plant just needs select nutrients, some water, and sunlight to grow. Not only do plants grow without soil, they often grow a lot better with their roots in water instead.
There are various different ways of growing things hydroponically. In one popular method, you stand your plants in a plastic trough and let a nutrient solution trickle past their roots (with the help of gravity and a pump). That's called the nutrient-film technique: the nutrient is like a kind of liquid conveyor belt-it's constantly sliding past the roots delivering to them the goodness they need. Alternatively, you can grow plants with their roots supported by a nutrient-enriched medium such as rockwool, sand, or vermiculite, which acts as a sterile substitute for soil. Another method is called aeroponics and it's typified by a popular product called the AeroGarden (see box below). Although the name suggests you're growing plants in air, the roots are actually suspended inside a container full of extremely humid air. Effectively, the roots grow in a nutrient-rich aerosol a bit like a cloud packed full of minerals.