Waves can take many forms, but there are two fundamental types of waves: longitudinal and transverse Both of these wave-types are traveling disturbances, but they are different because of the way that they travel. As a wave travels through a medium, the particles that make up the medium are disturbed from their resting, or equilibrium positions. In a longitudinal wave, the particles are disturbed in a direction parallel to the direction that the wave propagates. A longitudinal wave consists of compressions and rarefactions where particles are bunched together and spread out, respectively . For another view of this type of wave, take a look at the longitudinal wave video clip below. In a transverse wave, the particles are disturbed in a direction perpendicular to the direction that the wave propagates. The transverse wave video clip below provides a dynamic visualization of this type of wave. After either type of wave passes through a medium, the particles return to their equilibrium positions. Thus, waves travel through a medium with no net displacement of the particles in the medium.