A capacitor is a small piece of electrical hardware that can hold electrical energy within a circuit or field. Experts sometimes refer to capacitors as a type of internal battery or energy holder, although capacitors and batteries work differently. The dielectric or non-conducting substance in a capacitor separates two metal plates. The capacitor is often linked to a battery to take in the incoming electrons it produces. One way of saying this is that the capacitor slows down the amount of current and then distributes it according to what the circuit can handle. Manufacturers use materials including electrical conductors and insulating materials like glass or ceramics as capacitors.