Chakras (sank. wheel ) are energy centres .They are seated on the Sushunma-nadi. They are found on the astral body where the nadis cross each other.
Nadis are energy courses. The Prana ((life force) runs through these courses to the organs to make them work. The most important course is the Sushumna nadi. This nadi (course) starts at the bottom of the human spine and ends at the crown.
The nadi passes 7 chakras.
The higher chakras:
The lower chakras: