What are Chakras? Chakras are organizing centers for the reception, assimilation, and transmission of life energies.  Our Chakras, as core centers, form the coordinating network of our complicated mind/body system. From instinctual behavior to consciously planned strategies, from emotions to artistic creations, the chakras are the master programs that govern our life, loves, learning, and illumination. As seven vibratory modalities, the chakras form a mythical Rainbow Bridge, a connection channel linking the Heavens and Earth, mind and body, spirit and matter, past and future. From the great spiral galaxies, thousands of light years across, to the trillions of atoms swirling in a grain of sand, the universe is composed of spinning wheels of energy. Flowers, tree trunks, planets, and people – each is made of tiny wheels of turning inside, riding upon the great wheel of the Earth, spinning in its orbit through space. A fundamental building block of nature, the wheel is the circle of life flowing through all aspects of existence.

Chakra One: Located at the base of the spine, is associated with survival. Its element is earth.
Chakra Two: Located in the lower abdomen, is associated with emotion. Its element is water.
Chakra Three:  Located in the solar plexus, is associated with personal power, will, self-esteem. Its element is fire.
Chakra Four:  Located over the sternum, is associated with love. Its element is air.
Chakra Five:  Located in the throat, is associated with communication and creativity. Its element is sound.
Chakra Six:  Located in the center of the forehead, is associated with clairvoyance, intuition and imagination.  Its element is light.
Chakra Seven:  Located at the top of the head, is associated with knowledge, understanding and transcendent consciousness. Its element is thought.

The Heart Chakra is the central point of the Chakra System. Even in our language, the heart refers to the center of things, the essence, the kernel of truth, as in “to go to the heart of the matter”. This is a spiritual center, our core, the place that unites forces from above and below, within and without. The task of chakra four is to integrate and balance the various aspects of our being. In so doing, it brings a radiant sense of wholeness to the entire organism, an acceptance of the exquisite interpenetration of both spirit and matter. Within this sense of wholeness lie the seeds of inner peace.
The heart chakra is the center of love. Unlike chakra two, which is sexual and passionate and object oriented, the heart chakra is experienced within a state of being.  It is a divine presence of empathetic connection, rather than an extension of our need or desire. Love can emerge with a deep sense of peace that comes from lack of need, with a joyous acceptance of our place among all things, and the radiance that comes from inner harmony.

Anatomically, the heart chakra relates to the cardiac plexus and rules over the heart, lungs, and thymus gland.
Element of the heart chakra is air. Air is associated with freedom, openness, knowledge, falling in love, expansive and spirited, and letting go.  We hold too tight, we suffocate what we love, we give space or air, and it breaths.

Above information from Wheels of Life - Anodea Judith, PhD.
The Classic Guide to the Chakra system.