This chapter introduces the foundational passive circuit elements-resistors, capacitors, inductors, and the memristor. Kirchhoff’s laws are mentioned. Key concepts, including current, voltage, and power dissipation, are discussed in the context of circuits involving these elements. Both independent and dependent current and voltage sources are also covered and illustrated with practical examples. The chapter provides a detailed exploration of source transformations, supported by several examples, and introduces Thevenin’s and Norton’s theorems. Additionally, ideal amplifier concepts are presented to establish a basis for further study.