Hydroponics is a technique of growing plants without soil. What plants need to grow is water and nutrients. Hydroponics is especially useful in urban areas where space is a major issue.
The yield is almost three to five times more than what is grown in soil in the same area. One can do wonders in small areas too. The produce is also much more in a shorter duration if the nutrients are available at the right time and in the correct proportions.
Plants also remain healthier when growing in water as compared to the soil as the latter can easily get contaminated because for pollutants like fertilizers and pesticides. Since this is soil-less, lots of soil-borne diseases are avoided. This, in turn, avoids polluting soil because of spraying harmful pesticides and poisons.
In addition to water, nutrient rich matter like coco peat and pebbles are used as a medium to hold the plants in place.