Out Of Body Experience,what does it really mean?

What is an Out of Body Experience? What does it really mean?. Have you had any experience similar to it?

A friend of mine shared an Out of Body Experience she had few weeks ago and i was shocked. She narrated to me how she slept off in the afternoon and felt her spirit leave her body. Initially she didn't realize it was her spirit that left  until she tried  joining her cousins in the sitting room while they were playing but she couldn't. She tried all she could ,including yelling out to them but they couldn't hear her. Then she realized that there is something wrong and returned to the room only to see her body lying down on that same bed,same position ,still sleeping.To cut a long story short,my friend is alive and healthy after that experience.

 I had to use Google first to read an explanation from  any Scientist(they always have something to say) about an Out of Body Experience. That brought me to a whole new world of unexplained mysteries,i read peoples account of their experience and it was mind-blowing. 

Scientist also have an opinion about it,some wrote it of as lucid dreams,others called it hallucination ,some said it is the thin line between being awake and sleeping?.

Have you ever had an Out of Body Experience or you have your explanation of what it means? 
Please share with us.