Here's why:
* Longitudinal waves have vibrations that occur parallel to the direction the wave travels. Imagine a slinky: if you push one end, the compression (or rarefaction) travels along the slinky in the same direction as your push.
* Transverse waves have vibrations that are perpendicular to the direction the wave travels. Think of a wave on a string: the string moves up and down, but the wave travels horizontally.
Examples of longitudinal waves:
* Sound waves
* Seismic P-waves (pressure waves)
Examples of transverse waves:
* Light waves
* Water waves
* Seismic S-waves (shear waves)
