The word satsang signifies "gathering in truth". You must be wondering what the truth is. But this cannot be conveyed in words. Socrates said at the end of his life: I know that I know nothing. And even this statement fails do deliver the truth. Ancient advaita vedanta uses the terms real vs. unreal. Real is only that which is always present, what comes and goes it not real, according to vedanta. So what is that, which is always here - in our experience?
You must be wondering what the purpose of knowing that is. We could all agree on a fact that all human beings are looking for happiness. But we are looking for happiness in external objects. And how can something that is transient and unstable deliver us happiness? The only logical solution would be to look for happiness that is permanent. And this kind of happiness can be found, this is the good news. But we must look for it inside. And once we find it, we will realize that there is no difference between inside and outside, between me and you, between high and low, between man and woman. We will realize that everything is one undivided Reality and that we are one with that reality. Our real nature is existence-consciousness-bliss as the ancient Advaita vedanta declares.
This is the end of suffering and the beginning of real life - unimpeded by the constant chatter of egoic mind. The wave realised it was never separated from the ocean...

