Throw a stone in a calm water surface. The water particles are set in vibration at the point of disturbance. This particles cause neighboring particles to oscillate. These particles disturb their neighboring particles. Thus the disturbance, vibrations or energy is transfered through the surface of water. We can see circular waves spreading from the point of disturbance.
The wave is energy conducted through the medium using the vibrations of the particles of the medium. But the particles themselves are never displaced.
All mechanical waves likes sound waves, string waves,tsunami, earthquake moves in this fashion.When a political idea travels through the minds of the people , we call it a wave.