Once, a friend and I had a long and intens conversation. It was a warm summer afternoon and the door to the terrace was open. Over time, the conversation became gradually more and more silent and our minds became peaceful. At that point it started raining outside. We could hear the thick raindrops fall on the garden table and as I listened to the sound it became very clear to me that everything we had just talked about was just as relevant as the raindrops falling on the table - and of the same nature.
There is nothing the drops can do, nothing the rain can do, nothing the table can do to prevent the raindrops from falling on the table. Everything was completely at peace. At peace with itself, at peace with everything. This was nature's way and there wasn't a reason in the world to try and change it. Or even think of changing it. At that point all things were equal to themselves.
Someone spoke of non-duality. Others use words like Oneness and Wholeness. Other words that - within the limits of my capability of understanding - reflect the same essence are Truth, Authenticity, Nature of Mind, Buddha-mind, Buddha-nature, Ground Luminosity, Prajnaparamita, no-mind. It is, basically, the experience that we have when we see that things are equal to themselves. When there is direct perception of reality, without judgement, without ego, perhaps even without mind. Pure consiousness. Happiness.