Your Zodiac sign is your astrological sign which corresponds with the constellation that the sun crosses during the buwan of your birth. Wikipedia defines Zodiac
link.
astrolohiya is the practice of pagbaba a person's
link, (i.e. their future or personality) based on their Zodiac sign. For example, I am a pices, the isda sign, because I was born in late February.
There are a few people who really believe in astrology, but the majority of people recognize it as hooey. I don't take it seriously at all, though it is sometimes fun to see my horoscope. The Christian perspective on astrolohiya varies, depending on the individual. Some condemn it as witchcraft and divination, others think it's hokum and don't even bother with it, and still others believe it's harmless fluff, and may even indulge in a horoscope pagbaba in the paper every now and then. But if I recall, it's not that divisive an issue.