Capacitors are easy once you understand what they're used for. All a capacitor really does is... store energy! Duh! But how do they do that?

First, Capacitors block DC sine wave signals from a power source but not AC signals. This way, they can both charge and discharge as the circuit will allow. If a Capacitor has no energy in it, the resistance within the circuit will, temporarily, go to infinite ohms as the capacitor charges. This takes approximately 4 or 5 TCs (Time Constants) which is actually just fractions of a second. Nanoseconds.

Then, when the Capacitor is fully charged, it'll simply sit there with its charge, letting the current flow through the circuit/system as though it were never there. Once energy is cut off from the circuit is when it'll begin to discharge, acting almost like a power source itself! The formula for calculating Capacitance is this: C=Q/V, where Q is the charge on the conductor, V is the voltage, and C is the Capacitor itself.