Astrology is like looking at the stars in the sky and trying to understand what they mean. There are two ways to do this: sidereal and tropical astrology.
Sidereal astrology is like looking at the stars as they actually are in the sky - it's like a map of the stars. The stars move very slowly over a long period of time, so sidereal astrology takes into account the slight changes in the position of the stars over the years. This means that if you were born on a certain day, sidereal astrology uses the position of the stars on that day to determine what kind of person you are.
Tropical astrology, on the other hand, is more like a calendar. It divides the year into 12 equal parts, with each part being associated with a different sign of the zodiac (like Aries or Gemini). So if you were born between late March and late April, tropical astrology would say you are an Aries.
The difference between the two is that sidereal astrology uses the actual positions of the stars to determine your sign, while tropical astrology uses a fixed calendar. This means that over time, the two systems can get slightly out of sync - sidereal astrology might say you're a Virgo, while tropical astrology says you're a Libra.
Ultimately, both kinds of astrology are just ways of trying to understand our place in the universe. Some people find them helpful for understanding themselves and their relationships with others, while others think they're just a bunch of hooey.