The stored fundamental or natural oscillations are transformed and partially amplified and mirrored respectively by Merus. The overlaying of oscillations is called interference. The mathematical result of natural oscillation and interfering oscillation will be zero, if they are 180° phase-delayed and both have the same phase and amplitude. Resonance means that the amplitude of the natural oscillation is boosted by laying an additional in-phase oscillation onto the natural oscillation.
What can be done with resonance oscillations is well known. For instance a bridge will start to vibrate more and more if subjected to its resonance oscillation which may ultimately lead to the collapse of the bridge.