Imp: a mischievous child. They are unattractive creatures who are pictured wild and uncontrollable. (Germain folklore)
Brownie: They live in houses and help with household tasks. They work at night for little offerings of food (Scotland folklore, equal to the Scandinavian Tomte)
Elf: Little winged beings who can help humans or play trick on them. They have magical powers. (Norse and Germanic folklore)
Sprite: green beings with wings. Elemental spirit associated with water. They are joyful. (European folklore. Greek called Naiads)
Troll: They are hairy creatures living in caves or mountains. They are not very bright and may live in families. (Norse mythology and Scandinavian folklore)
Gnome: Dwarfs living underground and guarding treasures.
Dwarf: Small and ugly creatures living in mountains and earth. They are wise. They forge metal. They mine. (Germanic mythology)
Leprechaun: Mischievous old man clad in green coat who hide pots of gold. They make shoes and hide their gold under rainbows. (Irish folklore)
Hob: Household spirit. They can help around and can become a nuisance when offended. The best way to get rid of them is to give them new clothes. (Anglo-Scottish folklore)
Genie: a supernatural being that people cannot see. Sometimes grant wishes. (Islamic mythology)
Goblin: a grotesque and evil being.
Gremlin: mischievous creature who has a linking for aircrafts. They like to dismantle modern machines.
Fay or fae: enchanting creatures who are close to nature. Usually good, they can also be malicious. They are often portrayed with wings. They can leave fairy boons or fairy circles behind them. They can create a glamour, which is a very powerful magical illusion. Also called wee folks. (European folklore)
Changeling: a child exchanged for a fairy child.
Pixies: Inhabit ancient underground places like stone circles. They are childlike and love dancing. Piskies/piskeys or the little people.
Banshee: female messenger of death and the underworld. (Irish mythology)
Seelie or light fairy: they look for human help and return human kindness. They appear at twilight. They can play pranks on humans and are light-hearted.
Unseelie or dark fairy: they are ill-minded creatures. They assault travelers at night, picking them up through the air and beating them. They may get attached to a human. (Norse mythology)
Fairy and Other Spirits - Definitions
World of Froud