So I brought this up in the Dream View Academy IRC chat today with Opheliablue and she had never heard of it before, seems like a lot of people here haven't either so I figured I'd post the videos.

ReeceJones87 is incredibly knowledgable when it comes to Lucid Dreaming and has many great videos, his "Layers of Lucidity" is just one of his theories which personally, I think, should be generally adopted as standard Lucid Dreaming terminology.

The Layers of Lucidity easily define the different stages of lucidity. Instead of thinking lucidity as either "You are lucid" or "You aren't lucid", this theory takes into account the different types of lucidity. Such as only having control of yourself to having control of everything around you.

Below is the first video in the series where he starts talking about "Layer Zero", if you're interested in watching more there are five videos in total and the playlist is here: The 5 Layers of a Lucid Dream (1/5) - YouTube