You know, the basic function of the capacitor that is “blocking DC current but passing AC current”, which is why the capacitor is usually used in the circuit to separate DC current and let the AC current signal pass. Thus, capacitors, in the filter circuit, tuned circuit, coupling circuit, bypass circuit, time-delay circuit, shaping circuit and other circuits play an important role.

Meanwhile, the capacitor is able to form an LC resonant circuit with the inductor; And with the resistor, it can constitute an RC phase-shifting circuit. While it can be combined with an amplifier to form an LC oscillator or an RC oscillator.

BTW, there are many types of capacitors whose materials are also various. So the point is choosing different capacitors’ specifications based on different circuit requirements.