These two terms can sometimes cause confusion within the spiritual community. They are often used synonymously although there is a difference. They are not the same. The short explanation is:
Density – The Vibrational Frequency of Matter
Dimension – Is a Level of Awareness
The most basic life forms are water and minerals. They do have a consciousness and the matter they are comprised of, vibrates at the 1st frequency – therefore they are known as the 1st Density.
The plant and animal kingdoms operate from the 2nd Density, meaning their molecular makeup is vibrating at level 2 frequency. They too have a consciousness although they do not possess an ego – awareness of self.
Next on the evolutionary ladder are those of the 3rd Density who possess self-awareness known as ego. This is the density where humans begin. Those of the 3rd density do have self awareness, can remember the past, are cognizant of the future and able to feel separation. There are more densities but for this writing the focus is on the 1st, 2nd & 3rd.
A level of awareness. It is not a place to go physically, it is a state of consciousness. I once heard it described this way – Dimensions are the lens through which you perceive reality, or the way in which you define your reality.
The confusion arises because we can be in the same density and dimension at the same time or we can be living in one density and have a different level of awareness, meaning that we can be living in the 3rd Density and consciously operating in the 5th Dimension. We can live in a certain density but we do not have to be of that density.
Those souls who are operating at a very high ( 5th and above ) level of consciousness cannot comfortably live in the lower densities. When the difference between the two, density and dimension, becomes too great, a soul cannot survive in it.
We go forward from one dimensional level to another through the heart. If we are operating in the 4th dimension and wish to move up, we must learn to manage our ego, learn that the most powerful force in creation is Love, learn Unity consciousness and of course remember who we are and where we came from.