Chakras are energy centers… ancient yogis developed a concept of energy pathways running all around the body – rather than our energy just radomly ‘fuzzing’ about inside us. This is similar to the system of meridians used in Chinese medicine, reflexology and acupuncture.
One of the main energy pathways (nadis) is along the spine. Where pathways cross the spine, the energy is said to become greater and move in a circular motion hence the name ‘Chakra’, which means wheel in Sanskrit.
You can find more out about the Chakras on the following websites