there are several different types of faerie, not just the ones that reveal themselves as balls of light.
paraphrasing or quoting most of this from a book called witchcraft and practical magic
"Faeries take posession of the human world at night, and their flickering unearthly lights act as a warning to humans to keep away"
Faerie and Fey are offshoots of french and are replacements to the english word elf, which is interchangeable.
"pixie, elf, goblin, banshee, sidhe and leprechaun in ireland. fynadere on the isle of man, gruagach, urisk, brollachan and fuath in scotland. They range in height from the size of a human to minute proportions and their appearance varies from extreme beauty to grotesque ugliness."
faeries can lure people into their kingdom, or if they are particularly angry they may kidnap people.
there also are/were cults that worshipp(ed) the faeries.