There are twelve density layers of consciousness in existence. The third one is the physical world, the fourth is the spirit world, and the fifth is the realm of soul consciousness.
The higher numbers are more subtle, more expansive in their scale than the lower numbers. Each lower density layer is more compressed than the one above it and it is formed within the one above it.
Some people call these realms dimensions, which can cause confusion, as a dimension is actually something else. When referring to the twelve density layers, or realms, the technically accurate term is density. A dimension is not a location or a higher realm. A dimension is a measurable component of reality, such as length, width, height or time.
A density is a layer of compressed consciousness. It is a location within Creation. Instead of saying that you live in third density (the physical realm), you can abbreviate it to '3D,' provided you remember that, in this case, '3D' is short for third density, and not for three-dimensional.
The ultimate state of Infinite Being lies beyond twelfth density, as all densities are creations within its consciousness. The twelve density layers exist within the consciousness of Infinite Being.
The densities of immediate application to humanity are third, fourth and fifth densities.
3D: The physical realm
The physical world exists in 3D, or third density. Our minds are not limited to 3D, by any means. The global consciousness will go through a quantum shift when a critical mass in higher consciousness is reached. This critical mass will be achieved by a numerically small portion of the world's population because people with higher frequencies of consciousness have, proportionately, a much greater influence on the global mind atmosphere than do people who operate at lower frequencies of consciousness. As always, it will be the pioneers who change history.
4D: The spirit or astral realm
Throughout recorded history, fourth density has been the spirit or astral realm. 4D can be subdivided into twelve sub-layers or overtones, referred to in the plural as spirit or astral realms. When a person passes on from their physical incarnation, they typically move into residence in the third or fourth overtone of 4D. While physical experience can generate issues of emotional separation, 4D is an integrative density where people work through a healing of their issues. Spiritual seekers soon discover that there are higher, more subtle overtones within 4D and move there to study the higher truths of the universe.
5D: The soul realm
When the time comes to move on from the 4D spirit world, people move up into 5D in order to begin planning the experiences that they want to explore in their next incarnation.
Think of this as a kind of destiny workshop, where all possibilities are examined until, finally, one course of action is decided upon.
In 5D, the viewpoint of the soul is much wider than the focused viewpoint of the conscious mind in 3D. In 5D, space and time are seen as an interwoven tapestry of possibilities. Souls, during their research, can actually insert themselves into any situation in which they are interested, regardless of when and where.
In 5D, you can experience any event at any location and any point in time. You can go back into history or go forward into probable futures. You can view all possible outcomes of every potential situation and how it interacts with the probable actions of others. It works because your soul senses the total energy of each situation, seeing everything that would unfold if it were acted out.
So, in 5D consciousness, you can view exactly how a future event is likely to materialize. You can see it, feel it, touch it and know what your thoughts and feelings will be at that time because you actually insert your consciousness into the experience of the future event.
Courtesy of Owen Waters, www.spiritualdynamics.net