Astrology is a belief system that was once thought to explain differences in personality and behaviour.
I’ve looked through the answers and haven’t found many that are good enough, so I’ll answer even though I’m not an expert.
Astrology is far more complicated than you realize.
Most people are aware of the Zodiac sign in which the sun was when they were born, as well as those stupid little fortunes known as “horoscopes.”
So, a horoscope is an analysis of where each planet was in the sky, how far apart they were from each other, what house they were in, and all of the meanings that came from those combinations at the exact time and place you were born.