Hydroponics very simply refers to growing plants in a nutrient solution — water with fertilizers. Some systems, called aggregate hydroponics also use a medium such as sand, gravel or peatmoss to support the plants. Liquid hydroponics have no medium other than the water/nutrient solution.
The process is so simple that just about anyone can do it at home. You can find supplies by searching the Internet for a hydroponics store. A beginner's kit will set you back about $50, while more elaborate set-ups run into the hundreds of dollars.
Cal Poly Pomona Professor Terry Fujimoto explains to Val Zavala how it all works in this two-minute video.