We know that the Zodiac is divided into 27 equal parts, each measuring 13°20`.They commence from Aries 0° and ends by Pisces 30° .The 27 divisions are called Nakshatras or Star constellations. They r Aswini, Bharanj krittka , Rohini , Mrigasira etc. Each star is ruled by a planet. A planet cannot give a result of an event . A planet holds a certain degree in a house that means the planet is under a star. For example if Sun in 10°30′ in Aries it is in Ketu Star Aswini. And Ketu sub. Sub or Sublord is the further division of 27 Nakshatras into 249 sub divisions. This sub lords r the final deciding factor of an event in life. A planet is like a hospital star lord the particular Department . And Sub is the doctor of that department who will tell u the disease u r suffering from will be curable or not.