Final answer:
In the context of seismic activity, shear or S-waves are a form of seismic wave that move rock particles from side to side. On the other hand, longitudinal or P-waves, which are akin to how sound waves move in air, cause rock particles to move back and forth in the direction of the wave's propagation.
Step-by-step explanation:
In the areas of geology and seismology, two significant types of seismic waves are considered - shear waves and longitudinal waves. Shear waves or S-waves, also known as transverse waves, move in a manner that the motion of the particles of the medium is at right angles to the direction of the wave. This type of wave causes the rock particles to move side to side.
Longitudinal waves, often referred to as P-waves or pressure waves, are the counterpart of shear waves in a seismic event. Similar to sound waves moving through air, they cause the particles in a medium to move parallel to the direction in which the wave is headed thereby giving rise to the notion of compression and decompression in the medium. This in turn gives us a hint on how sound waves operate - as the waves are in a compressional pattern, the particles of the medium are compressed and then decompressed or rarefied.
To put it simply, shear or S-waves move the rock particles from side to side, and longitudinal or P-waves move like sound waves travelling through the air.
Learn more about Seismic Waves