It is part of the Ashtavarga which indicates the positive points of the houses of a horoscope and the sum total of which indicates the strength of a horoscope as such. Bindus and Rekhas are an easy way of computing the strength of each house much before the time the computers came in and today we can calculate the exact strength of houses and planets as is explained in my blog. To my mind, Bindus and Rekhas are not reliable and that is part of the reason why we are losing the credibility of Astrology.
If you are so curious about Bindus read http://www.astrojyoti.com/lesson8.htm