The easy answer comes in one sentence: instead of using artificial chemical fertilizers or pesticides to boost yields, organic farming uses traditional, mostly natural methods to achieve the same ends.
But a negative definition—"no pesticides"—doesn't capture the positive essence of what organic farming is all about: organic farming isn't merely a matter of "not doing" something: it's about placing a healthy, vibrant, environment (human, animal, plant, and soil) at the heart of genuinely sustainable food production. That means organic farmers strive to treat their animals humanely (giving them "free range" and shunning the use of antibiotics, animal wormers, and other drugs), do what they can to reduce "food miles" between their fields and their consumers (both to promote local farming communities and to reduce fuel consumption during delivery), celebrate the variety (biodiversity) of plant and animal life by growing a wide range of produce, and do everything else they can to minimize the negative environmental impacts of what they do (including pollution, oil and other energy use, and their impact on global warming). The Soil Association (a leading UK promoter of organic farming) sums up this positive vision: "Organic farmers take a holistic, principled approach that respects and harnesses the power of natural processes to build positive health across the ecology of the farm.