A near-death experience is a personal experience associated with death or impending death. Have you ever had one, hopefully not!
I have not, but that sounds very scary.
They say there can be a feeling of detachment from the body, levitation, total peace, security, and/or the presence of light. 
I cannot even imagine how that would feel. what causes this?
They believe being that close to death comes from disturbed bodily multisensory integration. Basically the sensors in us are on overload 
That is so interesting. I hope I never experience that.
I hope not either. Now the last explanation was the science definition. Religious beliefs say it's the crossing over into the afterlife the people just don't make it all the way.
That one makes a little more sense. What else do you know?
injuries, climbers who had fallen from heights or other individuals who had come close to death (near drownings, accidents) was reported by Albert Heim. This was also the first time the phenomenon was described as clinical syndrome. In 1968 Celia Green published an analysis of 400 first-hand accounts of out-of-body experiences. This represented the first attempt to provide a taxonomy of such experiences, viewed simply as anomalous perceptual experiences, or hallucinations. In 1969, Swiss-American psychiatrist and pioneer in near-death
Near-death experience
A near-death experience (NDE) is a personal experience associated with death or impending death. When positive, such experiences may encompass a variety of sensations including detachment from the body, feelings of levitation, total serenity, security, warmth, the experience of absolute dissolution, and the presence of a light. When negative, such experiences may include sensations of torment and torture. NDEs are a recognized part of some transcendental and religious beliefs in an afterlife.
Different models have been described to