Back in the old days, astrology was considered a science as a branch of astronomy and it was taken very seriously. It wasn't until after the middle ages that things began to change. When the church and science began conflicting openly with each other, certain things that were once credible subjects were considered heresy if not downright diabolic, such as astrology.
In the past 50 years or so, astrology has seen a resurgence in the western hemisphere. It is still considered a science as well as an art by most practitioners today. It is a science because it is the study of the planets' influences on a person's chart as well as the world at large. It is an art because it is subject to interpretation. We astrologers realize that not everything we read is true and that it is always open to someone's opinion. On the other hand, there are certain things the community has learned which we can pretty much attest to being tried and true if not fully accurate.
I realize this is a rather vague answer, but it is a difficult subject to pin down simply because of the differences of opinion. I myself find astrology fascinating and even though I have been studying it for over 20 years, I still find new and interesting things to learn. Astrology, when you get down to it, is very complex. It is so much more than what you read in the daily newspaper. Each person is unique and therefore the influence of the planets will affect them differently. We are not just our Sun Signs, we are much, much more.
Many people do not realize just how deep you can go with astrology, and they chalk it up to being mumbo jumbo simply because they do not see beyond the typical subject matter of a daily sun sign horoscope. With so many false astrologers out there today trying to get your money, I do not blame these people for not realizing that there is much more to astrology.
If you are truly interested in astrology, may I suggest you get a personalized chart done by a reputable and professional astrologer? You will see the difference. For a list of some astrologers in your area, visit the American Federation of Astrologer's website: http://www.astrologers.com/
Good luck to you and may the stars guide you!