Vargas (divisional charts) are one of Pārāśara's most distinctive contributions. The idea: take a single graha's position in the rāśi-cakra (D1), then divide that 30° sign into N parts (where N = 9 for navāṃśa, 10 for daśāṃśa, 12 for dvādaśāṃśa, etc.) and re-map. The graha's varga-position is its position in the N-times-zoomed-in chart. Each varga then 'reveals' the graha's behaviour in a specific life-domain.
BPHS Ch. 8 enumerates the 16 vargas with computational rules. Ch. 10 (Varga-viveka) tells you which varga to consult for which question — D9 for marriage and fortune, D10 for career, D7 for children, D12 for parents, D60 for past-life carry-over. Ch. 9 introduces the vargottama condition: when a graha occupies the same rāśi in D1 and D9, it gains substantial strength. This is one of the most-checked dignity conditions in interpretive practice.