Fairies is a both a broad term and a specific term. Broadly it refers to naturee spirits who watch over plants, the earth, water bodies, mountains and wild places. Much like spirit guides and angels watch over animals and humans, fairies watch over the plant and earth realm. These nature spirits are called different things by various cultures. Countries with a Celtic background refer to them as fairies, while those with a Germanic background use terms like elves or dwarves and gnomes, in Japan they are yokai and in Spain duende. Every culture has stories of these nature spirits, just with different names and tales specific to their area.
Specifically fairies are a term for what is often seen as small winged spirits connected to plants. Everything from flowers, herbs and bushes - they watch over plants of all kinds. They prefer wild places, but will hang around gardens too. They especially love gardens that have a bit of a wildness to them and are not overly manicured.
My mother grew up in England where she was often told to watch for the fairies at the bottom of the garden. Fairies are not necessarily the benign creatures of Victorian lore. Just like people some are nicer than others. Some are helpful, and some have less good intentions. Many are mischievous and like to misplace things on people. It is important to remember that they are plant spirits, so their agendas are different from ours.
Specifically fairies can be divided into the Seelie and Unseelie court. The Seekie court is connected more to flowers, herbs and gardens and they are mischievous but generally benign to people. The Unseelie court is connected to forests, bogs and swamps and can be malevolent towards people. It is understandable that they would not want people disturbing their homes. We have had a history of disturbing and destroying those places, so it can be understood why they are unhappy with us.
There are also trooping and solitary fairies. Trooping fairies are groups of fairies who wander about the countryside and sometimes form settlements. People sometimes have sighted them dancing or walking in groups.There are also solitary fairies who live on their own and are not connected to a group.
Pixies are small childlike fairies, usually without wings, often wearing green and with pointy ears. Pixies are known for being mischievous troublemakers. They are particularly associated with the areas of Cornwall and Devon. They watch over the moorlands, barroes and stone circles. They apparently do not get on well with other fairies.
Sprites are elemental spirits associated with air, fire and water. They are often seen as small wispy beings of light. They have a wispy translucent nature to them. They are associated with open meadows and small bodies of water.