Now, whenever I asked this question, my teachers either responded with a diagram of a wave like this (psst! it doesn't move in real life, I didn't go to Hogwarts.): or often referred to the analogy of water waves (when you drop something in water, the wave goes outward). But when we talk about a particle, like an electron, being a wave, or sound waves, what exactly does that mean? Sound waves, as far as know, compress and contract air particles and we represent that contraction and compression via waves-- wherever compression is high, we have the wave more in the negative axis (or any other convention that we might choose). Is this correct? What about a particle being a wave? Neither is there a sea of particles which bounce in their respective places which gives us the graph of a wave, nor are electrons emitted out of their orbits via which, we'd measure the frequency of their emission and represent it in a graph. So, what exactly does it mean for a particle being a wave, or for that matter, sound?