That's a good question defygravity, and also a very controversial one, with some people, and even courses like the Bradley Thompson ripoff Dream Course, saying that there is no such thing as Astral Projection, that it is all a dream.

Anyone who has ever woke up in the middle of the night to find themself floating over their body looking back at themselves laying on their bed, or has felt themselves come tumbling back into their body after having been out of it, knows that Astral Projection or Out of body experiences do exist though.

The main difference I find between Astral Projection and Lucid Dreaming is that with Lucid Dreaming a persons spirit is still inside their body and they are in control of their dream, whereas with an Astral Projection or an Out of body experience, a persons spirit is outside of their body.

Dreams of floating or flying, even though they may not even be lucid dreams can sometimes be astral projections as the persons spirit may be outside of their body floating or flying around.

My last lucid dream turned into an Astral Projection when I felt myself float out of my body, after which I was able to float around my house a bit and go through some walls.

The biggest problem I had while I was out of body was being able to see as everything was so dark, whereas while I was in the lucid dreams I had no problem seeing since it was a dream.