First, the properties of conductors and dielectrics are defined and considered in general in this chapter. Additionally, this chapter includes a description of the conductor skin depth, wire conductor resistance and inductance (internal and external), which depend primarily on frequency. In terms of frequency, conductor resistance R and inductance L are separated into two groups: DC/low-frequency conductor resistance and high-frequency conductor resistance and inductance. Additionally, herein, the properties of nonideal electronic passive components, such as nonideal resistors R, nonideal capacitors C, and nonideal inductors L, are explained and compared to those of ideal R, C, and L components with the same designated values. In particular, the R, C, and L components behave nonideally at high frequencies, whereas the same components behave ideally at DC and close to ideally at very low frequencies.