Ashtakavarga is a classical point system: each of seven planets and the Lagna gives a bindu (point) to certain signs, counted from its own position. A house's total (Sarvashtakavarga) shows how supported it is (28 or more is classically strong, under 25 needs support), and is also used to judge transits through that sign.

Every tool uses the same chart and the same classical rules as your full Kundli report, so the results always agree with your reading.