A capacitor is a device that stores electrical energy in an electrical field by virtue of accumulating charges on two close surfaces insulated from each other [1]. It consists of two conductors separated by a non-conductive region which can be vacuum or an insulator material known as [[Dielectric|dielectric]].
For a capacitor, the capacitance is measured as:
$$ C = dQ / dV $$
where,
Practically, a capacitor is a device that is capable of storing electrical energy and releasing it at a predetermined rate. It also blocks direct current, only allowing alternating current to pass through [2].
[1] https://en.wikipedia.org/wiki/Capacitor [2] https://www.electronicshub.org/bypass-capacitor-tutorial/