Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 1 · Basics and Panchanga
ज्योतिषमूलं पञ्चाङ्गं च
त्रिस्कंधं ज्यौतिषं शास्त्रं चतुर्लक्षमुदाहृतम् ।गणितं जातकं विप्र संहितास्कंधसंज्ञिताः ॥ २ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 54, verse 2.
The science of jyotisha (astrology) has three skandhas (branches) and is said to hold four lakh verses. O Brahmin, the branches are called ganita (maths of the planets), jataka (birth chart reading) and samhita (world events astrology).
Simple meaning: Astrology has three branches: planet maths, birth chart reading, and world events.
गणिते परिकर्मादि खगमध्यस्फुटक्रिंये ।
Planet maths covers basic sums, true planet positions, eclipses, and risings and settings.
छाया शृङ्गोन्नतियुती पातसाधानमीरितम् ।
Planet maths also covers shadows and the Moon's horns. Birth charts cover the kinds of signs and planets.
निषेकजन्मारिष्टानि ह्यायुर्दायो दशाक्रमः ।
Birth charts cover birth, life span, planet periods, livelihood, point tables and royal combinations.