Consciousness is obvious, mysterious, unthinkable, and infinitely deep. Scientists and philosophers often write convoluted exhausting boring explanations of consciousness; but that is not consciousness.
Consciousness' luminous reality is to be intuited directly and effortlessly. Consider the Dzogchen teachings. Tsoknyi Rinpoche sums it up brilliantly: “Let the display of thoughts, emotions, and perceptions unfold naturally and without clinging, like clouds passing through an open sky.” Consciousness is like the sky – open to everything passing through it but ultimately unaffected. Like a mirror – it reflects everything that passes by while staying clear and empty.
We live mostly in separation consciousness; feeling-thinking "this or that" in a world of distinct, somewhat unrelated objects. Me and you. Us and them. Light and dark - and shades in-between.
The universe is infused with consciousness. But it is unfocused and not self-aware. Life becomes progressively more intelligent until it become self-aware, self-conscious. Feeding back on itself. Learning from its own successes and mistakes.
Unitive, union, or cosmic consciousness is a state of alive luminous oneness. This state is more likely to persist while discursive dualistic thought is suspended.
At one extreme it a bath of bliss. And, we care little for the “details” of maintaining the body.
In a more ordinary functional life, we feel love and unity with others while still aware of separate persons and objects.