Astrology (from Greek: αστρολογ?α = ?στρον, astron, “star” + λ?γος, logos, “word”) is any of several traditions or systems in which knowledge of the apparent positions of celestial bodies is held to be useful in understanding, interpreting, and organizing knowledge about reality and human existence on earth. It is classified as a pseudoscience because it makes use of observed data about the heavens to draw conclusions that are unsupported by science. All astrological traditions are based on the relative positions and movements of various real and construed celestial bodies as seen at the time and place of the birth or other event being studied. These are chiefly the Sun, Moon, planets, Ascendant & Midheaven axes, and the lunar nodes. A practitioner of astrology is called an astrologer, or sometimes an astrologist.
Many of those who practice astrology believe the positions of certain celestial bodies either influence or correlate with people’s personality traits, important events in their lives, and even physical characteristics.
Astrology is not considered to be a science, but is more appropriately a spiritual discipline, and is separate from astronomy, the scientific study of outer space. For many astrologers the purported relationship between the celestial bodies and events on earth need not be causal, nor even scientific. Although there are astrologers who try to put astrology on sound scientific grounds, for many more it is a technology and an art that merges calculations with intuitive perceptions.
For more detail: http://en.wikipedia.org/wiki/Astrology