They have not gone onto the next level, the light, heaven, whatever you choose to call it. They remain behind, here on earth, and they account for many ghost sightings and haunted places. The reasons for this are varied. Some are complicated and unique to that spirit and others are simple to understand and relate too. I will discuss a few of the most common reasons that a spirit remains earthbound.
Some spirits remain at or near the site of their death, especially if it was sudden and unexpected.
They remain confused and don't know or accept that they have died. These spirits remain in the area and try to make contact with anyone that passes by that is sensitive to spirits. This type of spirit can be found almost anywhere a death has occurred. Sometimes a spirit realizes that it is dead and that life continues beyond that. They do not go to the light for reasons such as the fear that their existence will end, fear of the unknown, fear of going to hell or being judged for past deeds.