Chit is what you really are—pure consciousness. It is unchanging and undying and if you realize yourself as Chit, you become immortal (rather, you realize that you are immortal and always were). Chit identified with body and mind appears to be mortal. Note that the bodies are mortal—equally for the jnani and ajnani. Ramakrishna, Christ and Buddha—all had physical bodies and those bodies are gone, just as our bodies will perish one day. But as Chit we are immortal. This is to be realized and this is the Upanishadic ideal of moksha or freedom.