A capacitor is an electronic component that stores electrical energy for a short time. It does this using two conductive plates separated by an insulating material called a dielectric.
What capacitors do in circuits
Capacitors can smooth power, filter noise, store small bursts of energy, block direct current while allowing changing signals, and help create timing circuits when paired with a resistor.
Capacitance and units
The amount a capacitor can store is called capacitance, measured in farads. In everyday electronics, values are often much smaller than one farad, such as microfarads, nanofarads, or picofarads.
A capacitor is not a battery, but it can hold and release charge quickly inside a circuit.