RF/microwave MLCs reduce ESR, raise Q values

What is a capacitor?
A capacitor (formerly called condenser) is a passive electronic component that consists of a pair of conductors separated by an insulator called dielectric. When a potential difference (voltage) exists across the conductors, an electric field is present in the dielectric. This field stores energy and produces a mechanical force between the conductors. The effect is greatest when there is a narrow separation between large areas of conductor, hence capacitor conductors are often called plates.
An ideal capacitor is characterized by a single constant value, capacitance, measured in farads. This is the ratio of the electric charge on each conductor to the potential difference between them.