Dragonflies are insects, belonging to Odonata and Anisoptera. Adult dragonflies are characterized by large eyes, two pairs of strong and transparent wings, sometimes with color patches and slender bodies. Dragonflies may be mistaken for Zygoptera, which has similar structure but usually lighter structure. However, most dragonflies keep their wings straight and away from their bodies, while dragonflies fold their wings into a static state, along or above their abdomen. Dragonflies are agile fliers, while douniangs are weak and fly. Many dragonflies produce bright iridescent or metallic colors through structural coloring, which makes them attractive in flight. The compound eyes of adult dragonflies have nearly 24000 eyeballs.

In protodonata, fossils of the ancestors of large dragonflies were found in the upper Carboniferous rocks 325 million years ago (Mya). These aircraft have a wingspan of up to 750 mm (30 in). There are about 3000 kinds of Anisoptera in the world today. Most of them are tropical, and there are few species in temperate areas.

Dragonflies are predators in the aquatic larval stage. They are called nymphs or Na, also known as adults. The fairy lived in fresh water for several years. Adults may only stay for a few days or weeks. They are fast, agile aircraft that sometimes migrate across the sea and are often found near the water. They have unique and complex reproductive methods, including indirect insemination, delayed fertilization and sperm competition. During the mating process, the male grabs the back of the female's head or chest, and the female curls her abdomen under her body to absorb sperm from the second genitalia at the front of the male's abdomen, forming a "heart" or "roller" position.