The 16 Shodashavarga charts — each magnifies one area of life. D-9 for marriage, D-10 for career, D-24 for education, D-60 for past karma.
Divisional charts, or vargas, are finer harmonic charts derived from your main birth chart (D-1). Each varga magnifies one area of life: the D-9 navamsa for marriage and dharma, the D-10 dasamsa for career, the D-7 for children, the D-24 for education, and the D-60 shashtiamsa for past-life karma — sixteen in all.
A planet that looks strong in the main chart but weak in the relevant varga rarely delivers its full promise there, which is why classical astrologers always cross-check the varga before judging a house. Browsing them together shows which life areas are reinforced and which need support.
The navamsa (D-9) is the most important divisional chart, used chiefly for marriage, the spouse and the inner strength of every planet. A planet strong in both D-1 and D-9 is considered especially powerful.
The classical Parashari system uses sixteen vargas (the Shodasavarga), from the D-1 rashi to the D-60 shashtiamsa, each tied to a specific area of life.
Because a varga shows a planet’s strength in a specific domain. A planet may sit well in the main chart yet be weak in, say, the career D-10 — the varga catches that.