Vimshottari Dasha is a system of planetary periods used in Vedic astrology to predict an individual's life events. It divides a person's life into segments ruled by different planets, each lasting a specific number of years. The cycle lasts for 120 years, with each planet having a designated time frame based on its significance and influence. The system is based on the position of the Moon at the time of birth, which determines the starting point of the dasha. Each planetary period, or dasha, can reveal insights into various aspects of life, including career, relationships, and health, helping astrologers provide guidance and predictions.