Final answer:
A wave that displaces particles of the medium perpendicular to its direction of travel is a transverse wave, not to be confused with a longitudinal wave, where displacement is parallel.
Step-by-step explanation:
A wave that travels through a medium and displaces the particles perpendicular to the direction in which the wave is traveling is known as a transverse wave. This is because in a transverse wave, the motion of the particles of the medium is at right angles to the direction of the wave’s propagation. In contrast, a longitudinal wave displaces particles parallel to the wave's direction of travel. An example of a transverse wave is when a person moves a rope up and down to create ripples that move horizontally, while the motion in the rope is vertical. Longitudinal waves include sound waves, where particles vibrate back and forth along the direction the sound is moving.