Limited part of sky within which planets are seen is called zodiac. Tropical Zodiac is based on orientation of Earth to Sun.Zodiac measured from point of vernal equinox (apparent position of Sun at the commencement of Spring), which moves in relation to the fixed stars is called movable or Tropical Zodiac.
The orientation of equinoxes to the stars changes over time according to the procession of the Earth to its axis. Orientation of the Earth related to a fixed stars makes a complete circuit of the zodiac over a period around 25 000 years.
The zodiac, which corresponds to the actual constellations or the fixed stars, is called Sidereal Zodiac. This type of zodiac is used in Vedic astrology.
Ayanamsha mean difference between tropical and sidereal zodiacs. This term defines difference between point of vernal equinox in fixed stars and that of first point of the constellation Aries. There is controversy among astrologers on exact degrees and minutes of the Ayanamsha (more exactly, - what to count as a starting point of Aries). Lahiri Ayanamsha (21 degree and 10 minutes) is used as a standard by the government of India.
Natural benefics are Jupiter (Guru), Venus (Shukra), Moon (Chandra) and Mercury (Buddha).
Natural malefics are Saturn (Shani), Rahu, Sun (Surya), Mars (Kuja) and Ketu.