They're believed to be some sort of paranormal entities that take on the forms of children aged 6-16. Apparently they travel in pairs, and can be seen together walking down streets or doorsteps. They're not dangerous, according to the stories that people have shared, and no one can agree if they're aliens, vampires or ghosts.
If I had to pick one? I'd say alien, but it's not as if I believe in any of it anyway.