The energy crisis and environmental issues have led to the need for integration of energy systems with the aim of efficient use of energy sources to supply different energy demands. For this aim, optimal switching among different conventional and renewable energy sources should be scheduled to enable different energy systems to efficiently meet the energy demands in every sector of the whole energy system. The vector coupling of energy systems is challenging due to technical and economic barriers. Therefore, the first stage is to answer the question that what is the concept and definition of vector coupling of energy systems and related challenges to achieve whole energy systems? and what enabling technologies are required to integrate different energy systems?