Hydroponics is soilless agriculture: plants grow with their roots in nutrient-rich water (or inert substrate like coco coir or rockwool) rather than soil. The technique enables year-round production, precise control over nutrients, dramatic water efficiency compared to conventional farming, and vertical / indoor production unsuited to traditional agriculture.
Common for leafy greens (lettuce, herbs), tomatoes, and strawberries. Organic certification is contested — USDA currently allows certified-organic hydroponics, but traditional organic advocates argue that soil is central to the definition.