Vedic astrology means Super Natural Science. Science which can tell us about the past present and future. For example medical science can talk about the present state of a patient but astrology tells us when it will happen in future. Astrology defines the axis of planets, their speeds, their physical structures in respect with human lives. According to India Astrology there are five very important parts of Indian Astrology system:

a. Hora b. Sidhant c. Sanhita d. Prashna e. Shakun

These 5 branches of astrology are known as Skandh Panch.

Skandh panch is the study of all the branches of sciences Cosmology, Biology, Physics and Chemistry.

Hora: Another famous word for it is Jatak Shastra. Hora shastra is particularly related to our regular life. With the help of horoscope all the events of our life can be predicted for e.g. timing of marriage, timing of changing a job or when to get promotion, when one should go abroad etc.

Siddhant/ Mathematics: All types of mathematical calculations related to constellations and planets comes under the branch of Siddhant Shastra. Majorly the time calculations of solar and lunar months, calculation of speed and distance of all the planets and constellations and various axis calculations for planets comes under the siddhant shastra.

Sanhita: Sanhita Shastra provides the timing of earthquakes, heavy rains or no rains, natural calamities, harvesting would be good or bad, any kind of volcano eruptions, drought etc.

Prashna Shashtra:  This shastra gives you the quick answers for your question. Initially on the basis of the letters of the asked question, an astrologer used to give answers. But it was in the 5^th and 6^th century only. But later on 3 different siddhant entered:-

1. Prashn-akshar Siddhant

2. Prashna Lagan

3. Swar Vigyan Siddhant

Shakun: The another word for Shakun Shastra is Nimitt Shastra. In the century of 10^th, 11^th and 12^th this shastra developed independently otherwise it was a part of Sanhita initially. The famous scriptures which comes under shakun shastra are Vasantraj Shakun and Adbhuth Sagar. Even today when we start a work, we generally take care of auspicious day and muhurat to get good results.