According to Osho, satchidanandghan Paramatma is the inner, changeless center of consciousness—the witness from which seeing and hearing happen—whose nature is sat (eternal being that never changes), chit (unbroken awareness untouched by bodily states), and ananda (intrinsic bliss). It is the base before birth and after death, the still presence amid all passing phenomena.
It’s the unchanging real you inside that is always awake and peaceful, even while your body and thoughts keep changing.
From the Discourses
Passages where Osho speaks to this question — each links to the complete discourse.
Anand means bliss and citta means mind -- bliss mind. In English you don't have many words for the mind but in Sanskrit we have many words for the mind to denote different qualities. The only way to translate citta is. mind with a capital 'M'. It is not ordinary mind, it is the cosmic Mind. Mind with a lower case 'm' is the ordinary mind; Mind with a capital 'M' is the cosmic Mind. It is neither yours nor mine, it is everybody's Mind: not only of human beings but of trees, animals, birds, and rocks and stars. There is a Mind that supports all, there is a Mind that is the very substance of the whole of existence. This existence is made of citta stuff, mind stuff.
Surrender the ego -- it is only a false notion. I ask my sannyasins to give to me that which you don't have, so that I can give you that which you already have. Give your ego to me so that you can have the whole. 'Why remain tethered to a small thing? This whole universe is an organic unity. That is the meaning of Sampurna and that has to be dis-covered. Unless you discover it life is meaningless and a meaningless misery -- on one hand meaningless, on the other hand miserable. It is just an exercise in utter futility. But it all depends on you -- you can drop the ego in a single moment of understanding, just as one drops one's clothes -- because it is a false idea. Clothes are far more real.
Anand means bliss, nijo means individuality. Individuality is your essential core. Individuality is not your personality. Personality is given to you by the family, the society, culture; individuality is that which you bring into the world -- that is your original face. The individuality gets lost in many layers of personality, and a man has many personalities. You have one personality with your father, another with your mother, another still with your wife, another with your child, another with your servant, still another with your boss. You have many personalities, you have many faces, because you need different faces with different people in different situations. So personality is just a changing flux around you. It is like the surface of a lake, continuously wavering, waving, rippling. It is not its depth. It is constantly at the mercy of the winds.
Bliss is the taste of God. We cannot touch God but we can taste him. We cannot hold him but we can feel him. God is not a thing, so there is no way to encounter God as an object. God is your own subjectivity. It is the one who looks from your very center into the outside world. It is the one who is hearing me right now. It is the one who is conscious within you. Remember that consciousness is the door to God. And also remember that when you enter that door your whole being feels a tremendously blissful state which you have never known before. All happinesses fade away before it. All joys known before appear like toys. When you know the real thing, for the first time everything unreal is recognized as unreal; and before God is known all is unreal.
Atma means self, and anand means bliss; self bliss. And by self is not meant the ego. By self is meant your innermost core which is absolutely egoless -- your pure self, uncontaminated by the idea of 'I'... undefined by the idea of 'I'. The 'I' is just an arbitrary thing. It is needed -- it will be difficult not to use it -- but to become it is dangerous. It is just a label for social use. The moment you close your eyes, there need not be any 'I'. It is needed in relationship. When you are in relationship with a 'thou', the 'I' is needed. It is a term to relate to. When you are not concerned with the 'thou' and you are absolutely alone, the 'I' is not needed.