Sanskrit name for Horary astrology is "Prashna Tantra". "Prashna" means question and "Tantra" means teaching or science (or more precisely "continuum").This branch of Astrology is used for answering questions, which can be of any type. They are usually concerned with whether a person will achieve success in particular venture.
This branch of astrology is much more popular in India, then natal astrology. There are several reasons for that. First, it is a science, which allows to manage attunement of human activities with cosmic law. Achievement of this harmony allows to be successful in all actions on different levels.
Second, it is more specific then natal astrology.Any number of horary readings can be done for a client, while natal readings are usually done once. Third, this type of reading can be done even without information about client's time of birth.