What is astrology?
Astrology is the ancient science dealing with analysis of the in-born personality traits of the native, his strengths and weaknesses and prediction of what lies in store for him in life based on the placement of various planets in different houses of his birth-chart, which is commonly referred to as his Horoscope or janm-kundali. Though the science of astrology has been invented in various parts of the world during the course of human civilization, it attained its highest glory in India in the hands of such legends as Maharishi Bhrigu, Maharishi Parashar, Maharishi Jamini  and others. The most widely practiced system of astrology in north India is the Vedic astrology. A slightly modified version of north Indian Vedic astrology is in vogue in the Southern part of the country, whereas western system is practiced in western countries.
There are close relationships between astrology and astronomy as both these sciences are based on an accurate assessment of the movement of planets across the celestial sphere, although there are important differences between the two too. In astrology, this sphere is divided into 12 equal parts referred to as “rashis”, astrological signs which act “houses” for the nine planets passing through these signs during the course of their journey across the celestial sphere. The planets are the Mercury, Venus, Mars, Jupitar, Saturn.  Sun and Moon are also treated as planets. Besides, Rahu and Ketu, the shadow planets which represent the nodes of the elliptical orbit of the apparent movement of the sun around the earth. Thus, there are nine planets in all. Though the planets are celestial entities, in astrology, they behave much like human beings. They have their unique characteristics representing forces and elements of nature affecting human lives in myriad ways. They share relations of friendship and enmity among themselves. One or two house(s) are “owned” by all planets except Rahu and Ketu. They feel exalted, comfortable, agitated, disturbed, anguished etc depending on which house they happen to be in. Their behaviour also varies depending on whether they are in the company of  and/or sighted by friendly or enemy planets  during a particular period. A correct reading of the final outcome of such placement of planets is the key to making accurate predictions.
Many people dub astrology as pseudoscience and a belief in predictions based on astrological calculations as superstitions, typical of “unscientific” mind. This criticism, however, is not fair as different systems of learning adopts their own methods which are essentially different, and a system of learning cannot be dubbed as false or unscientific merely because it follows a particular system. 
         Astrology has proved its worth and usefulness over the centuries throughout the world. Based on the calculations of the movement of various planets through different constellations and houses, astrological predictions forewarn the native of the impending disaster, if the planetary orientation in the coming times indicates a negative outcome for the native. This is akin to forewarning a motorist of the potholes on the road ahead and other pitfalls awaiting him. Such a warning serves the important purpose of mentally preparing the native well in advance and enabling him to take adequate remedial measures. For example, if before embarking on a treacherous road trip in a hilly area, I am told in advance of the adverse traffic conditions and pitfalls, I can negotiate those potholes and dangerous curves more dexterously and save myself. Similarly, while currently passing through a tough time facing financial and relationship issues, an astrologer predicts that happy days full of abundance and love will come in the next six months or so, it gives me optimism and courage to face my current predicament with greater determination and hope. 
Astrology also teaches me to accept certain things as fait acompli. If some adverse happenings are predicted, the realization that these things are unavoidable gives me some semblance of consolation besides affording me an opportunity to mentally prepare myself to face the same with courage and determination. In the similar vein, a prediction of an adverse planetary combination in the coming times in terms of my relationships prepares me to be careful,  avoid situations of quarrel and control my temper, thereby enabling me to manage my relationships in a much better way than I would have without the benefit pf such predictions. To be forewarned is to be forearmed.