From earliest times, man looked to the sky, wondered and observed. Eventually patterns emerged, such as the fact that certain days came along which were exactly equal in day and night time, and that they corresponded to when it was time to sow the crops, or gather them. Naturally, we are now able to learn that the orbit of the earth around the sun brings changes in seasons. But back then, they believed that the position of the celestial bodies dictated certain events on earth. And from that concept astrology emerged. They (astronomy and astrology) were basically one and the same (many famous astronomers performed astrological predictions) until the discovery that the earth orbited the sun.
This is the point where astronomy and astrology parted, because astrology dictated that the earth was the center of the universe, which is technically inaccurate. Astronomy is based on science, facts, data, and logical reasoning. Astrology is not based in facts or science, it is now more entertainment and a subject of belief for those who so wish.