The chakras ("wheels" in Sanskrit) are spinning vortices of energy traditionally used as points of meditation by ancient yogis. There are many different beliefs on the number of chakras we have as indeed there are many different systems. Some speak of the six chakras and discount the Sahasrara or "crown" as a chakra, seeing it as a more overarching energy centre as the seat of the soul, other systems talk of eight chakras, five or three ... and it goes on. Each have their own validity and own form of practice. At the moment I work with the more widely known modern system of the seven chakras in the west, but continue to research and expand my understanding of the chakras and their potential. In the system I use the chakras are situated where the feminine (lunar) and masculine (solar) energy lines (nadis), known as Ida and Pingala respectively, meet and crossover on the body at certain points on the main cerebrospinal axis nadi known as Sushumna. The image of the Caduceus of Hermes widely recognised in the west relates to the same concept.
Chakras can be likened to areas of data / karma storage and receptivity in the energy field (aura). They have the ability to modify the content they contain at any given time if the owner is willing, but with more serious toxic buildups in the system this can take quite some effort and dedication to heal. You can work to optimise the functioning of your chakras via a variety of methods including yogic meditation and internalisation of seed mantra sounds associated with each chakra (the original and surely most effective way according to the ancient yogis), other forms of eastern spiritual practice such as qigong and tai chi, eating a healthy diet and visiting an energy healer (such as myself) where divine source energy is transmitted into the chakras and other parts of the subtle anatomy. Chakras work on multiple levels and have many layers to them, they are therefore one of the most comprehensive systems gifted to humans and can reveal the depths of a person's soul, health and attitude to life. It is true to say that they are really little understood in modern times as is the case with many of the true ancient practices as they were not often documented it seems, but instead handed down verbally and kept secret between teacher and pupil.
Below is a brief summary seven chakras as known in the western tradition where aspects of organ and bodily function are associated alongside psychological effects. You can find a little more detail in my book The Chakra Kitchen: Feed your Body to Nourish your Spirit and there are many more comprehensive published works on the chakras. In my Chakra Sessions I offer a full assessment of your individual system and offer guidance on healing where there are imbalances. The chakras always work as a team and the functionality of each will affect the others.
Root (Muladhara) - 1st chakra
Our first chakra, known as the most physical of the chakras, is associated with supporting our immune and skeletal systems, gonads and general physical wellbeing. It is also said to be our centre of security, survival, family and tribal traditions both local and global. The root chakra is at the base of the spine with the perineum being an important activation point. This is traditionally seen as a predominantly masculine chakra ruled by the planet Saturn (it has both masculine and feminine influences from the intersecting nadis and the astrological signs of Capricorn and Aquarius that rule it). It is also the seat of the coiled serpent or Kundalini energy and it is from here that we begin our spiritual journey up the spinal ladder to the divine. The overarching element associated with the Root chakra is Earth. It resonates with the colours red, black and other "earthy" tones.
Sacral (Svadhisthana) - 2nd chakra
The second chakra is associated with supporting our reproductive organs, lower back, urinary tract, large intestine, hips and the lymphatics. It governs our one to one relationships with people and our attitude to power in these areas. The sacral chakra is overall feminine in nature and ruled by the planet Jupiter (it has both masculine and feminine influences from the intersecting nadis and the astrological signs of Saggitarius and Pisces that rule it). Some say this is also a masculine chakra due to Jupiter rulership and also being a more physical chakra like the Root and Solar Plexus chakras. This chakra is associated with the dark centre of the womb, our true seat of creative power. It is located just below the navel area through to the sacrum bone and resonates with the colour orange. The primary element of the Sacral chakra is water.
Solar Plexus (Manipura) - 3rd chakra
Our third chakra develops supports our stomach, upper intestines, gallbladder, pancreas, liver, middle spine and adrenals. It is the centre associated with our self-will, self-esteem and ability to facilitate transformation. The solar plexus chakra is the home of ego and masculine in nature ruled by the planet Mars (it has both masculine and feminine influences from the intersecting nadis and the astrological signs of Aries and Scorpio that rule it). The element primarily associated with this chakra is Fire. It is located just above the navel area and resonates with the colours yellow and gold.
Heart (Anahata) - 4th chakra
The fourth chakra supports our heart, cardiovascular system and the thymus. It is the centre associated with unconditional love and compassion. It is predominantly feminine in nature and ruled by the planet Venus (it does have both masculine and feminine influences from the intersecting nadis and the astrological signs of Taurus and Libra that rule it). The heart chakra is located in the centre of the chest area and resonates with the colours green and pink and is feminine in nature. The predominant element associated with this chakra is Air.
Throat (Visuddha) - 5th chakra
The fifth chakra supports the throat, oesophagus, neck, mouth, teeth, ears, thyroid and parathyroids. This chakra is where we make all our choices and where we express ourselves and listen to others, it governs our sense of taste and discernment. The throat chakra has the important role of connecting the body with the head. Mercury is the ruling planet and the gender is predominantly masculine although some would say this is a feminine zone being an upper chakra (it does have both masculine and feminine influences from the intersecting nadis and the astrological signs of Gemini and Virgo that rule it). It is located in the centre of the throat and resonates with the colours sky blue, aqua and turquoise and is masculine in nature. Ether is the element associated with the Throat chakra.
Brow (Ajna) - 6th chakra
The sixth chakra links us to the mental body and supports the brain, neurological system, the eyes, nose and pituitary and pineal glands. The Brow chakra is often seen as feminine in nature and ruled by Moon, but can actually be seen as the meeting point of the Moon and the Sun as planetary rulers and the zodiac signs of Cancer and Leo respectively, thus creating a gender neutral zone - this is certainly true of the six chakra system where the Crown is not a chakra. It is our psychic centre of intuition, wisdom and insight. It is located above and in between the eyes and resonates with the colours dark blue and indigo. Light is often classed as an "extra" element associated with this chakra.
Crown (Sahasrara) -7th chakra
The crown chakra supports the skin, muscular and central nervous systems. It is our connection to the divine, the seat of the soul, all that is and our gateway to "life-force" which nourishes our mind, body and spirit. This chakra is located at the top of the head and resonates with the colours violet, white and clear quartz. In the seven chakra system the Sun is often said to rule this chakra rather than as a co-ruler of the Brow and that would give it a predominantly masculine nature, but the general consensus is that the Crown is genderless being the centre of divinity and unity/oneness - consciousness is assigned as "extra" element here.
As an addendum note I would like to say that in my own research and understanding of the chakras there are many contradictions in the literature. It has become a complex web of astrological, psychological and medical associations with gender and elemental theories thrown into the mix throughout the ages. Here and in my book introduction to The Chakra Kitchen, I am giving a brief outline of the most popular beliefs and it is easy to get into a twist on what is correct and incorrect information - the trick is to learn to discern for yourself, see what resonates. I believe that it is only with dedication and practice going in to ones own system that deeper insight can be gained on a personal and collective level, which I have no doubt was what the ancient yogis and evolved ancestors did in the first place.