Natural and artificial ingredients are both used to add (or preserve) flavor, color, and texture. They may also be used to fortify processed foods with additional vitamins and minerals or other nutrients.
According to the United States Food and Drug Administration (FDA), natural ingredients are derived from natural sources. You might see ingredients such as beet powder, lecithin, garlic powder, black pepper, spices or vitamin C; all of which have been extracted from plants.
Most plant-derived natural ingredients can be listed as a group on a food label using the words 'natural ingredients,' but that's not true for animal-based ingredients, which must be identified individually (even though animals are very natural beings). Hydrolyzed vegetable proteins and monosodium glutamate (MSG) must also be identified individually on an ingredient list.
Artificial ingredients are created in laboratories. Examples include many food colorings and artificial sweeteners. Ascorbic acid, which is the scientific name for vitamin C, might come from a lab instead extracted from a plant. In that case, it's an artificial ingredient.
The words 'natural ingredients' certainly sound healthier than 'artificial ingredients,' but there may not be much, if any, difference between the two types of ingredients.
Artificial ingredients must be approved for use by government agencies such as the FDA. Plus, those ingredients only make up a very small part of the total processed food (and that processed food may not be good for you whether or not the artificial ingredients are present).
Vitamins may be artificially created in a lab (such as ascorbic acid and folic acid, the synthetic form of folate), and even through they're not natural, they're still beneficial.
The word 'natural' doesn't mean the product is organic. It may or may not be -- while organic foods are natural, not all natural ingredients are organic, and many natural ingredients are extracted with chemical solvents and other processes that are not allowed in true organic foods.
If you wish to avoid artificial ingredients, you can look at the list of ingredients printed on any packaged foods (or just avoid most packaged processed foods). You can buy fresh fruits and vegetables, or fresh meats and seafood that have not been processed beyond simple packaging.
It's not too difficult to avoid artificial ingredients at home, but many restaurants use processed foods that contain artificial ingredients, except for a few places that specialize in natural and organic dishes.
United States Department of Agriculture. "Food Safety: Natural Flavorings on Meat and Poultry Labels." Accessed July 27, 2010. http://www.fsis.usda.gov/Help/FAQs_Flavorings/index.asp.
United States Food and Drug Administration. "Food Ingredients and Colors." Accessed July 27, 2010. http://www.fda.gov/food/foodingredientspackaging/ucm094211.htm#qanatural.
United States Food and Drug Administration. "Food Label Helps Consumers Make Healthier Choices." Accessed July 27, 2010. http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm094536.htm.