In this chapter we summarize the essential principles associated with electrostatic and magnetic phenomena caused by electric charges and currents, respectively, based on the E-B analogy. In addition, equipotential surface in electric phenomena and equivector potential surface in magnetic phenomena are compared to widen the area that this analogy covers. These are necessary to understand the usefulness of introducing superconductivity into electromagnetism, which will be done in Chap. 3 . The Poynting vector, which will be used to discuss the flow of energy in other chapters, is also described. It is recommended that readers who have not studied electromagnetism for many years read this chapter before proceeding to the next chapter. Since this chapter is compactly summarized, it will be actively utilized further on.