Planets in the solar system are like an accurate clock in the sky. Their revolutions and movements are very precise. Planets rise and set at definite times. Effects of certain planetary influences are plainly visible such as day and night, change of seasons and tidal effects. It surely have influence on everyday life of all of us. But subtle effects on people are not so clearly evident at a glance.
Astrology is a system of observations gathered through ages. For an example Vedic Astrologey was founded by Sage Parashara thousands of years ago and the observations collected through ages are the essence of the Hindu Astrology.
Astrology, both Eastern and Western are based on a predictive system very similar to to the one used by meteorology. Instead of forecasting the weather conditions, Astrological predictive system indicates such and such things are highly probable to happen to the people when such and such planetary positions are prevailing.