Buddha taught that everything depends on the mind. To understand what this means we have to know the nature and functions of the mind. At first glance it may seem easy, because we all have mind and we recognize our mental states: we know how we are, if we are happy or unhappy, if we have clear ideas or we are confused, and so on. However, mind if someone asked us how it works and what its nature, it is most likely that we did not know an appropriate response, indicating that in fact we do not know what is.
Some people think that the mind is the brain or some other part or function of the body, but this is incorrect. The brain is a physical object that can be seen, photographed and subjected to a surgical operation. Instead, the mind is not a material object and can not see, photograph or operate. Therefore, the brain is not the mind, but another part of the body.
There is nothing in our bodies that can be identified with our minds because they are different entities. For example, while our body is relaxed and immobile, our mind may be occupied with various thoughts, which indicates that our body and mind are not the same entity. In the Buddhist scriptures compared to a hostel body and mind with a guest. At the time of death, the mind leaves the body and travels to the next life, as the guest leaves the hostel and moved to another place.
If the mind is not the brain or other body part, then what is? It is an immaterial continuum that functions to perceive and understand objects. Because the mind is not a physical phenomenon and formless, material objects can not obstruct it. For our body to reach the moon has to travel in a spaceship, while the mind can move to that place in a single instant thought. Knowledge and perception of objects is a function of the mind. Although we say "I know this or that," in reality it is our mind which apprehends objects. We know the phenomena with the mind.