Tank circuit is composed of a combination of capacitors and inductors.(the right part)
exciting this circuit initially by switching on then off a DC voltage source will result in energy being stored and exchanged in form of oscillating voltage and current. Simply, like the pendulum where the energy is being stored and exchanged in the form of oscillating elevation and speed.
What makes it special is that the rate of oscillation (frequency) is unique for a given combination of L and C and depends on the size of them, and not on the amount of energy.
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Start the simulation with the switch being closed. thus ensure that the capacitor is fully charged and the inductor is uncharged.
Open the switch and notice how the capacitor start to discharge (its voltage being decreased) while the inductor is charging (current is increase) until the capacitor reaches zero voltage and the inductor is fully charged now. then the inductor discharge into the capacitor again.
This process is continue at a specific frequency for ever in this ideal situation. which is not true in real world where the stray resistance for capacitor, inductor and wires connecting them dissipate energy in form of heat, and the amplitude of oscillation decay over time.
