What kind of wave is characterized by compressions and rarefactions?

A wave characterized by compressions and rarefactions is a longitudinal wave. In a longitudinal wave, the particles of the medium move parallel to the direction of the wave's propagation. This causes regions of high pressure, called compressions, where the particles are close together, and regions of low pressure, known as rarefactions, where the particles are spread apart.

Many familiar examples of longitudinal waves are found in sound waves, which travel through a medium such as air, water, or solids. However, while sound waves are indeed longitudinal, the term ‘longitudinal wave’ itself is a broader classification that specifically pertains to this behavior of particle movement. In contrast, transverse waves, such as light waves or waves on a string, have particles that move perpendicular to the direction of wave travel, resulting in different characteristics and behaviors. Electromagnetic waves consist of oscillating electric and magnetic fields, which do not involve the particle movement typical in mechanical waves like sound or longitudinal waves.