Chakra is a Sanskrit word meaning ‘wheel’. The individual chakras are part of a greater network of subtle energies. Information about them is found mainly in the Upanishads, where four texts in particular describe their locations, and provide symbolic descriptions of each chakra.
In the 10th century, the Guru Goraknath wrote another famous text: the Gorakshashatakam. He was believed to be a saint and he set out practical knowledge for the benefit of his disciples. This text provided new information concerning the powers that accompany the awakening of the chakras, and established the connection between chakra awakening, and the practice of meditation.
The most detailed and comprehensive study of the chakras is contained in the sixth chapter of the Sat-Cakra-Nirupana, in the major work of Shri-tattva-Cintamini, composed by the Purananda Svami. Written in the 16th century, it contained descriptions and illustrations of the chakras.
As mentioned, the chakras are part of a greater network of subtle energies, and we are unable to isolate them without violating holistic principles. Our physical make-up is well researched through the many body-based Western sciences. But our personal, subtle make-up can only be explored through quite different means of involvement, rather than through clinical detachment, and a holistic frame of reference. Some advanced meditation techniques like binaural beats can help us to get involved with our inner-self holistically.
However, the physical and non-physical aspects of the human being are two aspects of the same whole. They cannot be separated, and we cannot study one without reference to the other. We are unable to study the subtle energetic anatomy without seeing its relationship to the physical anatomy. Likewise, we are unable to study the physical anatomy without including the knowledge of the subtle anatomy.