This amazing video explains the difference between the 3D, 4D and 5th dimensions.
'We use a twelve-dimensional model and you, sitting here in a physical body exist in the 3rd dimension: it is matter-based.
The 4th dimension is called the astral plane: it is basically emotionally-based. Together, these two dimensions make up what is called the Lower Creation World. These are the dimensions where the game of separation is carried out. These are the only dimensions in which illusion of good and evil (duality) can be maintained and in which you can feel separated from Spirit and each other.
The planet is vibrating at the level of the mid-astral so it is beginning to feel like a dream state...for many. You are never quite sure if you are awake or asleep. Continuities are breaking down. You'll notice that your dream-states are changing, that as you wake up you are not quite sure if you are awake. You will become lucid while you are dreaming, fully conscious in that state. You will be fully self-aware as you move back and forth between different realities, and all of them will feel equally real to you. It won't seem like there is only one true reality, anymore.
The 5th through the 9th dimensions make up the Mid-Creation Realm, in the model we use. The 5th dimension is the Lightbody dimension, in which you are aware of yourself as a master and a multidimensional being. May of you have come from this plane to be Lightworkers here.'
This text is an excerpt from What is Lightbody by Tachira Tachi-Ren, Archangel Ariel.