A dragonfly is an insect belonging to the order Odonata, the suborder Epiprocta or, in the strict sense, the infraorder Anisoptera. It is characterized by large multifaceted eyes, two pairs of strong transparent wings, and an elongated body.

The Damselfly (Suborder Zygoptera) is an insect in the Order Odonata. Damselflies are similar to dragonflies, but the adults can be differentiated by the fact that the wings of most damselflies are held along the body when at rest. Furthermore, the hind wing of the damselfly is essentially similar to the forewing, while the hind wing of the dragonfly broadens near the base, caudal to the connecting point at the body. Damselflies are also usually smaller, weaker fliers than dragonflies, and their eyes are separated.

Damselflies undergo incomplete metamorphosis, with an aquatic nymph stage. The female lays eggs in water, sometimes in underwater vegetation, or high in trees in bromeliads and other water-filled cavities. Nymphs are carnivorous, feeding on daphnia, mosquito larvae, and various other small aquatic organisms. The gills of damselfly nymphs are large and external, resembling three fins at the end of the abdomen. After molting several times, the winged adult emerges and eats flies, mosquitoes, and other small insects. Some of the larger tropical species are known to feed on spiders, hovering near the web and simply plucking the spider from its perch there.

Dragonflies have excellent eyesight. Their compound eyes have up to 30,000 facets, each of which is a separate light-sensing organ or ommatidium, arranged to give nearly a 360° field of vision. Odonates are completely harmless - they do not sting or bite. Indeed, they are beneficial in the same respect spiders and other predators are beneficial - they keep the burgeoning insect population in check. Many of these species prey on each other; I often see dragonflies with damsels in their clutches. Dragonflies are among the most ancient of living creatures. Fossil records, clearly recognizable as the ancestors of our present day odonates, go back to Carboniferous times which means that the insects were flying more than 300 million years ago, predating dinosaurs by over 100 million years and birds by some 150 million.

Much larger dragonfly species existed in the distant past than occur on earth today. The largest, found as a fossil, is an extinct Protodonata named Meganeura monyi from the Permian period, with a wingspan of 70-75 cm (27.5-29.5 in). This compares to 19 cm (7.5 in) for the largest modern species of odonates, the Hawaiian endemic dragonfly, Anax strenuus. The smallest modern species recorded is the libellulid dragonfly, Nannophya pygmaea from east Asia with a wingspan of only 20 mm, or about ¾ of an inch. Dragonflies are the world's fastest insects and, although estimates of their speed vary wildly, most credible authorities say they are capable of reaching speeds of between 30 and 60 km/h (19 to 38 mph). A study showed that dragonflies can travel as much as 85 miles in one day.