Consciousness is an irreducible primary. It cannot be defined or reduced into more basic concepts.
If you try to analyse what it is to be aware, you will soon discover that no analysis is possible. Aside from giving synonyms, the only terms that are available for your analysis are much too general. For instance, you might say that to be conscious of something is to be “in contact” with it. But chairs are in contact with the floor without awareness—so, what kind of contact is conscious contact? Or, you might try saying that awareness is a causal response. But the earth is causally responding to the sun. So, what makes something a conscious causal response? Consciousness. That’s all we can say. There is no further analysis.1