Inductors and Capacitors in AC Circuits

A capacitor stores voltage, acting as an open circuit (blocks off signal) at lower frequencies, and acts as a short at higher frequencies (lets signal pass).

An inductor, on the other hand, stores current, acting in exactly the opposite way of a capacitor. Inductors act as shorts at lower frequencies, and open circuits at high frequencies.

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A resonant circuit can also act as a filter.
A series resonant circuit with a C and L has low impedance to the resonant circuit.  This is because the impedance of the Inductor and the impedance of the capacitor cancel each other out.  With Zero impedance, current is maximum.
In contrast, in a parallel (tank) resonant circuit, impedance is highest.  This is because, as the capacitor discharges current, the inductor receives this charge.  Therefore the current cancels each other out.  Then we have zero current, and therefore maximum impedance.