Hydroponics, in principle, is actually very much like normal gardening, except you're doing it without soil. Since there's no soil for roots to grab onto to support the plant above ground, larger hydroponic plants must be supported either with external supports or provided a soil-less growth medium where roots can spread. Smaller plants like leafy greens often rest on a flat surface to support the leaves, while the roots and base of the plant emerge through holes in the support board.
The hydroponics part of the equation is the manner in which water and nutrients are supplied. With roots exposed to the air or entangled in a growing medium, it's up to the grower to ensure that each plant gets a chance to absorb the optimum amount of water and nutrients. This may be accomplished by running a constant stream of water through the lower root zone, by periodically flooding and draining the root zones, or even by fogging or misting the roots at carefully timed intervals.
