Sidereal vs tropical zodiac
Western astrology uses the tropical zodiac tied to equinoxes. Jyotish uses the sidereal zodiac tied to the fixed constellations, shifted by about 24 degrees (ayanamsha).
That is why your Sun sign in a Vedic chart is often different from your Western sign.
The nine grahas
A classical Vedic chart uses the Sun, Moon, Mars, Mercury, Jupiter, Venus, Saturn, Rahu and Ketu. Rahu and Ketu are the lunar nodes.
Each graha has its own nature, friendships, house significations and karmic meaning.
Lagna and houses
Lagna is the sign rising on the eastern horizon at birth. It sets the counting of the twelve houses.
Sign, house, dignity and aspects of the grahas form the core of interpretation.