That which is 'conscious'. In absolute terms, Chit is The Conscious.
'The Conscious' is also 'The Real'. Individual, Mind, senses, body are all conditionally conscious, whereas Chit is independently conscious.
Chit is the content of the 'I thought' (ahankara) or individuality. Chit is reflected by the I thought but not limited by it.
Chit is the ground consciousness that manifests in all subtle phenomena
like individuality, mind, senses, etc. Chit as ground consciousness is beyond all phenomena and is limitless.
As the limitless ground consciousness, Chit is called 'The Big' (Brahman). As the ground conscious underlying the reflected individual consciousness, Chit is called 'Inner Self' (atman).
Ground Consciousness is also called 'Space-like Consciousness' (Chidakasha). Reflected individual consciousness is called 'Appearance of Consciousness' (Chidabhasa).
Chit has a conscious nature hence is able to make the eye see, the ear hear, the mind think, and the prana breathe. Chit is the eye of the eye, ear of the ear, mind of the mind, and breath of the breath.
Chit reflected in the mind is responsible for the mind to know objects. Chit is not an object to be grasped the eye or mind. It is that because of which the eye and mind are grasped.
Then, how is Chit grasped? The question is baseless. Chit is not an inert object that needs to be reached through consciousness. Chit being the conscious entity is self evident (svatah siddha), self known (svayam jyoti). Chit is known it terms of direct (aparoksha) self-evidence . Chit is also known as the conscious nature that is reflected in the I thought (aham pratyaya vishaya).
Chit as the ground consciousness (atma) underlying the reflected individual consciousness (jiva) is the same as the ground consciousness (brahman) underlying the Creator consciousness (Ishwara). This atma is that brahman; I am brahman; you are that; consciousness is brahman; thus does Vedanta declare oneness of The Conscious.