Dragonflies do not sting and are not harmful to humans. They have an ovipositor that is lance-like and is needed to deposit the eggs in plant stems. If someone disturbs a dragonfly while it's laying eggs, the person may get lanced by the ovipositor.
While dragonflies do not sting, they can bite. Most dragonflies can't break the skin of humans, and if they do, it doesn't really hurt. Unless they are disturbed, dragonflies don't bite people.
Dragonflies live in proximity to lakes, rivers or wet areas where there are mosquitoes, flies and other small insects to eat. Dragonflies lay eggs in freshwater, where the larvae stay until adulthood.