Passive components are electronic components that do not require any external power source to operate, unlike active components (such as transistors and diodes) which require a power supply to control current. Passive components are used to manage and manipulate electrical signals and energy within a circuit. The key characteristic of passive components is that they cannot amplify or generate energy; they only store, dissipate, or transform it.

The most common types of passive components include resistors, capacitors, inductors, transformers, crystals, and piezoelectric devices. These components are essential in a wide variety of applications including signal processing, power management, energy storage, and voltage regulation.