Ignis fatuus

commonly known as "will o' the wisp"
In Sweden we call them "irrbloss". Loosely translated to "wandering flare", but the word "irra" means something more along the lines to "go astray"
They are seemingly aimlessly floating around. Either in search of something or to lead you somewhere. Either to a treasure, or to lure you into a watery grave in a swamp.

They are also believed to be the spirit of people who have moved the marker poles in the forest, making their own plot of land bigger. They are then called "Lyktgubbe," or in English "Lamp man/spirit."
They are forever bound to walk along the false border, moving the poles back and forth. Only way to set them free is to follow it, and move the poles back to their correct place.

Photo taken about 200m (650ft) away from my home.
Photoshopped last night.