The idea of waves can be best understood through the example of a stone thrown into still water. This act produces rings of small waves or ripples on the surface of the water. We can see them spread out in even, concentric circles, from the point where the stone falls. Depending on the size of the stone, the size of the circle also varies - the larger the object, the larger the waves. In this context, the movement of waves is produced by the up-and-down motion of particles in the water. Such waves are called transverse waves. Another example is the water waves in the ocean, which move up and down.

Sound waves, on the other hand, move in a different pattern. Their vibration is caused by the back-and-forth movement of particles. Such waves are called longitudinal waves. They travel in the same direction as the vibration, or disturbance that causes them. As the waves travel through a medium, the molecules or particles collide with each other in the same direction and the waves keep moving.