Consciousness is a common term consciously being used by all but it is very difficult to understand it. Consciousness is the fundamental principle of human life and existence. The understanding of consciousness keeps evolving day by day. Consciousness is being defined by very many theories from different perspectives. Here in this article, there is some basic information to have little knowledge of what is consciousness. When we delve into the concept of consciousness, we have the nature of consciousness, theories of consciousness, levels of consciousness and stages of consciousness. All these things combine together to give us basic knowledge about what is consciousness. As a whole, the main idea of many theories says that human consciousn...