I see formulas on the market that contain ingredients called DHA and ARA. What are these substances?

DHA is docosahexaenoic acid and ARA is arachidonic acid. Both are long-chain polyunsaturated fatty acids. The body can make DHA and ARA from certain other dietary fatty acids, which are found in plant oils and other sources; however, DHA and ARA are also consumed directly in the diet.

Source: FDA/CFSAN Office of Nutritional Products, Labeling and Dietary Supplements July 2002