Organic products are naturally grown without the assistance of synthetic chemical pesticides or fertilizers. Beyond this lack of unnatural chemicals in the food this method of farming is also meant to sustain the land and keep the surrounding ecosystems healthy. It is based on minimal use of off-farm inputs and on management practices that restore, maintain and enhance ecological harmony.
More formally, 'Organic' is a labeling term that denotes products produced under the authority of the Organic Foods Production Act. The principal guidelines for organic production are to use materials and practices that enhance the ecological balance of natural systems and that integrate the parts of the farming system into an ecological whole.
For a more detailed discussion, see this link, Organic Farming