Petroleum systems and its understanding is very crucial in exploration and production. It is an integral part of the exploration and production workflow. Since few decades with the advancement of technology and computing power for effective simulation of the geological models and its understanding, we are now able to test our hypothesis, do the uncertainty analysis of the data and derisk the prospectivity of the area of interest. With that integrated approach, a comprehensive review of all the category I and II basins total 13 in number in terms of all the aspects of the petroleum system is undertaken. The review is based on the understanding by different authors in each basin including that of ours during the last three decades. This chapter summarises different aspects of petroleum system elements and processes in each type of petroleum system in each basin. A classification of sources rocks e.g., speculative, effective, potential, biogenic etc. and in terms of types of kerogens was made. The understanding of each petroleum system also covers the onset of expulsion timing of each source rock contributing the hydrocarbons in those respective basins. The overall synthesis of each petroleum systems is broadly elaborated in terms of geological ages which gives an idea about regional scale effective source in basins of Western Continental (WCMI), Eastern Continental Margins of India (ECMI) and North East Margin of India (NEMI) along with Andaman, Vindhyan basins. In the Indian context, it is the first time comprehensive study which gives an idea about the present understanding of petroleum systems of Indian basin. It clearly brought out the types of sources contributing hydrocarbons in these basins, besides about the potential sources and the understanding of expulsion onset timing of each source in each of the documented petroleum system. This gives further clues to different elements and processes of petroleum systems, thus helping the geoscientists to further generate dataset in different domains for better understanding and calibrations of the individual petroleum system and ultimately will aid in exploration and production efforts in Indian basins.