Advaita means nondual or not two. This oneness is a fundamental quality of everything. Everything is a part of and made of one substance. Often the question arises, If it is all one thing why dont I experience it that way? This is confusing oneness for the appearance of sameness. Things can appear different without being separate. Just look at your hand for a moment. Your fingers are all different from each other, but are they separate? They all arise from the same hand.
It also turns out that everything that exists in the world including people, objects animals, and plants are connected at the source, even though they look and act differently. The oneness of Being has an unlimited number of different looking expressions that we then experience as different things.
Looking more closely at your own hand can reveal there are many similarities in the actual substance of your fingers. All of your fingers consist of of very similar skin, bones, muscles and even cells and atoms. When you explore your experience more fully, you may discover that all things are part of one infinite field of Being.
What about your experience right now? Is it possible to discover this subtle oneness in ordinary experience? It is, if you set aside the expectation of a dramatic experience of oneness and explore the oneness a little bit at a time. Just as even a single drop of water is wet, you can experience oneness in even simple everyday experiences, since oneness is a fundamental quality of everything that exists.
Let's try an experiment: just explore your fingers and your palm. Can you find where fingers start and the palm ends, or are they essentially one thing? And where does the hand stop and something else called the forearm begin? Can you see the connected oneness of your fingers, hand and forearm?
Now what about the other parts of your body? If you notice all of the connections, are your toes and your forehead really a part of one thing even though they look so different? And is there really a separation between your thinking and your brain. Where does your brain stop and then something else begin called a thought? What about emotions and wants? Are these subtle experiences really in any way separate from your body?
Now, notice the simple sensations you are having: the sounds you are hearing, the sensations of touch, and the objects and events you are seeing. If you are seeing something, where does the seeing stop and something else called the eye begin? If you are hearing sounds where does the sound start and the ear stop? Perhaps the hearing and the sound and your ear are all one thing. Yes, the ear is different from the sound, but in the act of hearing they become one thing.
Then, where does the source of the sound stop and the sound itself start? For example, if a bird is singing outside your window, where does the bird stop and the sound of its song begin? Or are they one thing? If the bird and its song are one thing, and your hearing and the song are really one thing, then is it possible that you and the bird are one thing also?
Advaita, or oneness of Being, is actually something quite ordinary and is not actually hidden and difficult to experience. Obviously a dramatic experience of oneness, where you are overwhelmed by the oneness of the whole universe, is a special experience. But why wait when this beautiful and fulfilling sense of oneness is always available right now?