What qualifies as lucid dreaming?

I always understood it was a kind of dream when the dreamer knows they are dreaming. I used to have these alot. I still do, occasionally. I've also had that thing where you wake up from a dream and think you're awake only to discover that you're still dreaming. Then there is that half sleep thing when I'm aware of being in my room and in the presence of something while not being able to move which can be scary. I've been told that I sleepwalk and sleep with my eyes open sometimes as well as talk in my sleep. I'm intrigued, as well, by what some might consider to be out of body type experiences. I don't believe that is what is actually happening, but it seems pretty real when it does. I love sleep.