The recent mass appearances of jellyfish in Korea have caused economic and social damage, as they plague swimmers and fishermen. However, jellyfish have high economic and nutritional value, and contain low levels of calories and hydrolysates. Thus, jellyfish are a natural, healthy food that can improve high blood pressure, bronchitis, and a multitude of other diseases. Here, we present research on the ecology, classification, bloom, damage caused, food component characterization, and tissues of jellyfish, with the aim of facilitating further study. Research on use of jellyfish as salted products, and for collagen and qniumucin would also be valuable. A jellyfish body is classified into three parts: the body, termed the umbrella; the oral arm; and the tentacle. Jellyfish are planktonic marine members of a group of invertebrate animals comprising the classes Schypozoa (phylum Cnidaria) and Cuboza. In Korea in 2012, jellyfish damage resulted in decreases of annual catch and commercial value estimated at 177 and 141 billion won, respectively. Because concentrations of heavy metals are below the safety limits for seafood, dried jellyfish appear to be safe raw materials for food. The proximate compositions of Nemopilema nomurai and Aurelia aurita were 97.1% and 96.5% moisture, 0.9% and 1.2% crude proteins, undetected and 0.1% crude lipids, and 1.7% and 1.8% ash, respectively. According to their total contents of essential, total, and non-essential amino acids, jellyfish gonads were deemed good-quality protein. Because the major functional components of jellyfish are collagen and qniumucin, jellyfish can be used salted, or these components of healthy diets can be extracted from them. For more effective use of jellyfish, unit costs should be decreased and safety guaranteed. Additionally, dehydrators attached to conveyor belts should be developed. Since jellyfish can be used throughout the year, they should be listed in the Korean Food Standards Codex as a food source.