Chakras are energy centers associated with bodies. Eastern or esoteric traditions have talked about them for a long time, and clairvoyant individuals will usually be able to perceive them and agree between themselves on what they see. Most people are able to easily learn to feel the energy of chakras.
Chakras are rotating vortexes where energy enters and exits. They might have different diameters depending on how much energy is going in and out. Each chakra relates to certain qualities and issues.
Most commonly, seven chakras are agreed upon, like this:
1. Root - relates to basic survival and security.
2. Navel - procreation, sex
3. Solar Plexus - feeling, one's sense of knowing, gut feeling
4. Heart - acceptance and love
5. Throat - one's ability to communicate
6. Forehead - 3rd eye, one's psychic perceptions
7. Crown - spiritual connection to higher levels of awareness.
It appears that there are also chakras outside the body. These will become more important as spiritual evolution increases, and as the human DNA structure evolves to be able to support these:
8. Outside body
10. Solar System
Each of these relate to the ability to deal with issues on a wider and wider scale. The chakras kind of act as anchor points, forming stable means of interacting with a certain sphere of life.