Astral projection, what is this world?

One day, a friend and I were talking about how sometimes when we wake up we are paralyzed and cannot move one bit and hear this static noise in our ears and sometimes have an out of body experience. We both thought that this was something normal that occurs with everyone every once in a while. When we talked to some more people about it, we realized that it's not so normal. I have these out of body experiences every once is a while, but I am not fully in control of myself when they occur. Only once was I ever fully in control and aware of what was happening. I thought we might be having seizures or something so my friend got to researching. We are basically experiencing what people describe as astral projection. Now, I don't know whether to think that astral projection occurs in the mind or that you're astral body is leaving your physical body. What do you think this is?