There are different definitions of the term consciousness, and much controversy surrounds the topic.
In spirituality, consciousness is referred to as the intelligence in Nature that is undifferentiated, that has not yet moved into form. It is intelligence before boundary, before memory. In the most fundamental sense, it is described as one of the building blocks of the universe. In any physical form, consciousness has already become differentiated and is perceived as a separate identity. In this view, your state of consciousness describes the degree to which you feel connected to the undifferentiated intelligence of Nature.
In Western science, consciousness is often referred to as a state of wakefulness or the contents of your awareness. By this definition, consciousness describes the substance of any experience that you have. Without consciousness, you couldn’t be aware of yourself, your inner world, or the world around you. Of course, the contents of your consciousness are subjective, and unique to you, which makes consciousness difficult to study by the scientific method. This implies that there is no such thing as objective reality because your individual consciousness is the filter through which you always perceive the outside world.