Prasna (Sanskrit: प्रश्न, "question") is Vedic horary astrology — the art of answering a specific question using the chart cast for the exact moment the question is asked.
Unlike natal astrology which requires a birth chart, Prasna only needs the time and place of the question.
The underlying principle: the moment a sincere question arises in the mind is cosmically significant — the planets at that instant hold the answer.