not physics. which is what I've asked.
I agree wholeheartedly. a Physicist should be able to explain most things without resort to complicated maths.
Try this: Either as a thought experiment or a real one.
Hang a very heavy weight to act as a pendulum.
Take your handkerchief and tie a knot in the end.
Attack the pendulum with your knotted kerchief by hitting the weight repeatedly with the knot, always in the same direction.
You will find that if you strike at random intervals, the pendulum will scarcely move.
If however you always strike at the same point in the motion of the pendulum the blows will add up and the oscillatory motion will increase.
Eventually you will be able to get a good steady swing going.
This is resonance (at very low frequency so you can see what is happening).
The weight is accepting small packets of energy at its resonant frequency. All these packets are reinforcing one and other so energy transfer is high.
You can also upset the oscillation by striking at the wrong moment - when the pendulum is going towards the knot. Do this enough times and you will slow or stop the oscillation.
If you want to demonstrate damping in this experiment use a piece of sponge rubber on a string. The sponge will introduce damping.