According to the FDA, there isn't any exact definition of "natural food." It generally suggests products that don't have "added color, artificial flavors, or synthetic substances" (2012).
"Organic food" is different from "natural food." It implies the process of producing the food with environmental-friendly farming methods, like without "synthetic pesticides, bioengineered genes, petroleum-based fertilizers and sewage sludge-based fertilizers" (Food Marketing Institute)
The U.S. Department of Agriculture (USDA) and its agents are the certifiers of organic food in the United States. For more information about where to get organic certification in and outside the U.S., click here.
Below is the table reflecting some differences between normal products and organic food from Mayo Clinic.