This chapter summarizes the essential electromagnetism needed to understand electric machine operation. It focuses on three fundamental laws of magnetic fields: Ampère's circuital law, Faraday's law of electromagnetic induction, and the Lorentz force law. These quantitatively explain the three core physical phenomena of electromechanical energy conversion—generation of magnetism from electricity, electricity from magnetism, and electromagnetic force—which will serve as the foundational framework throughout the book. The chapter introduces magnetic circuit analysis, presents the magnetic Ohm's law, and establishes the core concepts of self-inductance, mutual inductance, and flux linkage using a dual-coil model.