When the body enters the sleep paralysis stage and your waking consciousness can expand out of it; then you are no longer interacting with the actual world in a physical way. Consciousness is then experiencing the realms of potential reality. One might still be able to interact with the physical world, but it would be more difficult or tricky. I recall once while being out of my body and trying to walk through a wall. I could not do it and the feeling was as if being stuck in stretchy rubber. Then the thought occurred to me about being on the other side of the wall and it was instantaneous like teleportation … suddenly I was on the other side.
This answer originally appeared on this Quora question on Astral Projection.