They are synonyms. They are different words for the same thing…with perhaps minor differences. It is said the Eskimos have 50 words for snow. This might be a myth, but we have many English words for shades of the color blue (and I am removing the ones that have blue as part of the name – like baby blue): azure, celeste, cerulean, cyan, denim, glaucous, indigo, iris, periwinkle, sapphire, teal, turquoise, ultramarine, viridian, and zaffre. Then we have other languages in the world that use different terms for the color blue like azul in Spanish, glas in Welsh, mavi in Turkish, modra in Slovenian, bru in Sicilian, niebieski in Polish, and uliuli in Hawaiian to name a few.
There are countless words used for the same thing. Awareness and consciousness are two terms pointing at the same thing. That is what words are…merely pointers. Awareness and consciousness are not the only pointers. You could also use the term “Self”. The Self has even more equivalent pointers.
In Hinduism, Brahman is the ultimate reality. Atman means Self. It is said that Brahman is equivalent to Atman. That ultimate reality is the Self…which is awareness or consciousness. This is why you also hear some teachers say all there is is awareness or consciousness. Brahman is also God, so the Self is God. This is why some teachers say you are God…playing that you are not God in order to experience creation. Most teachers stay away from Everythingness as a term (probably because it is too long with too many syllables), but some teachers use Oneness as a term. We are all One…in God, as God…the Self.
In Buddhism, the teaching is everything is void or empty. This is not a contrary or different teaching, but a continuation and extension. So you could use the term emptiness, nothingness, or void for “ultimate reality”…which is the Self or awareness or consciousness. Eckhart Tolle uses the term space or spaciousness…which is in the same spirit of emptiness or void. It holds everything. You could use the pointer of stillness or silence as well. Stillness is not a foreign concept or pointer for Indian teachers, sadhus, and yogis.
Another common pointer is being. Not so much as a noun (which is looking for a “me”), but more as a verb. Being is what we always have been…our essence. Again, a pointer for Self. Another pointer is the Center…and then metaphorically the Heart. Abide in the Heart (the center of being)…which is the Self. Of course, this center is not geographical. Nicholas of Cusa said “God is an infinite circle whose center is everywhere and whose circumference is nowhere.” As said previously, the Self is Brahman which is God…so the Self is a circle whose center is everywhere and whose circumference is nowhere.
Of course, some people fixate on the term and attach to it. A pointer is like a finger pointing at the moon, but then people fixate and become attached to the finger instead of looking at the moon.
That is why the Buddha, who saw people attached to a self (a “me”), then taught anatman (no-self). Of course, he was talking about a continuing me…a personal self. When Buddhists started fixating and becoming attached to the void, later teachers started talking about voidless-void. The Heart Sutra taught Emptiness is Form and Form is Emptiness.
Teachers will sometimes choose a pointer that means the opposite of previous teachings (Atman…to anatman) or will combine opposite terms together to create a new pointer (voidless-void). I have sometimes described the Self as a pure potentiality…not something, but not nothing. I have also described the Self as changeless and ever-changing. Combining opposites can be a good pointer.
Sometimes, teachers will negate everything altogether…like Nagarjuna’s Four-fold Negation…it is not this, nor that, nor both, nor neither. The Self is said to be nondual, but nonduality is not two…nor one, nor nothing, nor any combination, nor all of these, nor none of these.
I hope you forgive the fireworks show, but I hope you get my point. There are many different terms/pointers used to point to the same thing…the Self…which could be called awareness or consciousness as well…or as some teachers called it, “That.” Tat tvam asi…that thou art…you are That.