Electional astrology — called Muhurta in the Vedic tradition — is the branch of astrology concerned with choosing the right moment to begin an action or endeavour. Where natal astrology reads the chart of a birth and horary astrology answers specific questions, electional astrology works forward in time: given that you want to do something, when is the best moment to do it?
The underlying premise is that every action begins under a sky, and that the sky at the moment of beginning imprints itself on the endeavour, shaping its development and outcome. A marriage begun under a strong, harmonious chart carries that harmony as a seed. A business launched under a chart dominated by difficult configurations carries those difficulties into its foundations.
This was not fringe thinking in the ancient and medieval world. Kings timed their coronations, military commanders timed their campaigns, merchants timed the signing of contracts and physicians timed the administration of medicines — all by reference to the planetary positions at the chosen moment. The tradition spans Babylonian, Greek, Arabic, Indian and European medieval astrology with remarkable consistency of principles.