A capacitor stores electrical energy using two conductive plates separated by an insulator (dielectric). Types: 1. **Ceramic** - Small, non-polarized, high-frequency use. 2. **Electrolytic** - Large capacitance, polarized, used in power supplies. 3. **Tantalum** - Stable, polarized, small size. 4. **Film** - Precise, stable, low loss. 5. **Supercapacitors** - Very high capacitance, energy storage. 6. **Variable** - Adjustable capacitance, used in tuning circuits.