What is the main function of a capacitor?

Hint:Capacitor is defined as an electrical equipment which stores and releases electrical energy into the circuit. It actually sends alternating current rather than sending direct current into the circuit. It is an integral part of any component and hence is found in almost all electrical circuits.

Complete step-by-step solution:
The primary use of a capacitor is to store electrostatic energy in an electric field and hence supply this energy whenever possible to the circuit. To prevent the circuit from being damaged, they only allow alternating current $\left( {A.C.} \right)$ to flow through them while restricting the direct current $\left( {D.C.} \right)$.
It actually works in the way that when it is connected to a charging circuit, it stores electrical energy but since it is removed from the charging circuit it dissipates energy and hence can be used as a temporary battery. Energy stored is the main application of a capacitor.
Some other uses involve-
(i) Power conditioning.
(ii) Coupling or decoupling of signals.
(iii) Filtering of electrical noise and remote sensing.
Capacitors are diversly used in various industries because of their different properties.
Additional information: There are different types of capacitors:
(1 ) Axial electrolytic: Small, low voltage, general purpose capacitor.
(2) High voltage disk ceramic: Small-size with high tolerance.
(3) High voltage electrolytic: Used in power supplies.
(4) Metalized polypropylene: Small-size, good for up to $2{\text{ }}microfarad$.
(5) Multi-layer: Surface mount, high capacitance.

Note:Capacitance is usually measured in the farad unit, which is the equivalent of one coulomb per volt. A coulomb is the unit of electrical charge. Both farad and coulomb are identified as standards by the International System of Units. The capacitance can be measured in microfarad for the capacitors in household electrical components.