Define and discuss the meaning of: to oscillate. To oscillate means to move back and forth in an even rhythmic manner as in the swinging of a pendulum. From the start of one swing to the start of next is one one oscillation.
Oscillations may be timed in terms of oscillations per minute, or getting faster, oscillations per second. As oscillations become faster (several per second and more) they are commonly referred to as vibrations. To introduce a technical physics term: one oscillation per second is one hertz; 20 oscillations per second is 20 herts, etc.
If at all possible, build the oscillator and perform the tests described in the text. (I hope someone will do this and provide a video.) In any case, have kids analyze why a rod, stretched string, or other device may oscillate/vibrate as it does. (In every case it will involve an ongoing exchange between kinetic and potential energy as in the bouncing ball.)