Fairies are small, humanoid magical creatures, typically standing between one and five inches in height. They possess a diminutive human body, head, and limbs, but are distinguished by their large, insect-like wings which may be transparent or multi-coloured. Despite their human-like appearance, fairies are not considered to be highly intelligent and cannot speak human languages. Instead, they communicate with each other through a high-pitched buzzing sound. They are known to be exceptionally vain creatures, and if left to their own devices, may spend hours preening and adjusting their appearance. This vanity is their most prominent personality trait.
Fairies possess a very weak form of magic which they primarily use to deter predators, such as the Augurey. Their magical abilities are limited, and they are not considered powerful enough for their body parts, such as their wings, to be used in serious magical applications like wand making. The primary “use” of fairies by the wizarding community is for decoration. Due to their harmless nature and attractive appearance, they are often summoned or placed on objects to create a lively and magical ambiance. Professor Flitwick, for instance, used live, fluttering fairies to decorate the Christmas trees in the Great Hall at Hogwarts. Fairies are oviparous, laying up to fifty eggs at a time on the undersides of leaves. The eggs hatch into brightly coloured larvae, which spin a cocoon and emerge as fully-formed winged adults six to ten days later (Fantastic Beasts and Where to Find Them).
Fairies are a known, if minor, part of the wizarding world.
Fairies primarily serve as a world-building element, highlighting the diversity of magical life and the often-casual, and sometimes exploitative, relationship that wizards have with less intelligent magical beings. Their depiction as vain, low-intelligence creatures subverts the common Muggle folklore image of fairies as benevolent, wise, or powerful beings, a recurring theme in the Harry Potter series where magical creatures often differ from their mythological counterparts.