The word consciousness is a reference to who/what we are. The emergence of the nonphysical dimension of ourselves. We are and have a body, but we are and have a consciousness as well that comes from the body.
The body can be seen externally, while consciousness is unseen and exists internally, expressed through our body externally. Consciousness is term used to refer to the inner domain that is from within our body, that emerges as a result of our brain. Without a physical brain or body, there is no non-physical (or metaphysical) consciousness for us to exist as.
Consciousness means to be with-knowledge. That is what the word means in it's original true meaning through etymology. It shares the same root with science, the Latin 'scio', which means knowledge. 'Con' mans together or with. '-ness' denotes an action, quality or state. Putting it all together, we get con + scio + ness, meaning the state of being with knowledge.
We are physical biological beings (bodies in existence), as well as psychological beings (consciousnesses in bodies). Other animals aren't human animals who have biological bodies as well, and they are psychological beings as well. Psychological beings have consciousness, although the degree of consciousness potential and how capabilities of consciousness can manifest and express themselves in a physical body differ.
Conscious beings can hold knowledge, to be with-knowledge in their consciousness, and use it to interact with the environment in existence to varying degrees of utility. Our biological unit of the body can store knowledge as well (such as with our cells), but has less agency and ability to interact and affect the existence around it without consciousness as an agent to move it.
Plants are also biological units as well, but don't have a psychological dimension and are limited to the knowledge of their cells to operate. Psychological and consciousness beings are able to interact and affect the world more with actions. Consciousness beings have more potential to change the world around them.