Smart grid (SG) is regarded as the next-generation intelligent power grid. Smart grid provides the necessary fundamentals for power control and management in microgrid, which is considered as an important emerging application in SG. This chapter presents an introduction to the important concepts and technologies in smart grid, from two main aspects: smart grid infrastructure and smart grid applications. The smart infrastructure includes smart power system, information technology, and communication system. And smart grid applications include fundamental applications, emerging applications, and derived applications.