Quite literally, the term "vardoger" is a Norwegian word defined as "a premonitory sound or sight of a person before he arrives."
Vardogers are a class of paranormal "doubles," a class that includes doppelgangers, crisis apparitions, and bilocation. In fact, it is believed that the vardoger is simply an example of bilocation.
Those who experience a vardoger "haunting" generally describe the phenomena in an almost identical manner. Generally, the witnesses are at a location, most often home, waiting for a friend or loved one to arrive. About 15 minutes to a half hour before the scheduled time of the person's arrival, the witness will hear the sounds associated with that person coming home. They will hear a car in the driveway, hear doors opening and closing, and even the footsteps in the entry way. Rarely, the actual car or the form of the person will be seen in solid form, indistinguishable from a real person.
My family went through its own period of vardoger hauntings in the late 1990s/early 2000s, especially concerning the arrival home of myself or my sister. In one specific textbook example, my mom and I were in the bedroom, waiting for my sister to come home from work. We heard the garage door open, a car door open then close, the garage door being lowered, and then the kitchen door being opened and closed. The dogs rushed out of the room towards the kitchen to greet my sister, and after calling to my sister where we were...my mother quickly followed, only to find that no one was there. No car was in the garage. After precisely 15 minutes, my sister did indeed arrive home, none the wiser to what had just occured.
It is theorized that in these vardoger cases, the spirit of the person, eager to arrive, does in fact leave the body to arrive early. And, although in a similar paranormal class, vardogers are distinctly different from the more widely known concept of a doppelganger. In classic doppelganger cases, the person himself often sees his own image. The doppelganger seems as flesh and blood as a real human, identical in every way save for one or two slightly different details to the "host." It is considered extremely unlucky, and even is seen as a death omen in some cultures, to see your own doppelganger. Vardogers, on the other hand, are benign and not associated with luck, good or bad.