Here's why:

* Longitudinal waves are waves where the particles of the medium vibrate parallel to the direction the wave travels. Imagine a slinky stretched out and you push one end. The compression and expansion (rarefaction) of the slinky travel down its length, and each coil of the slinky moves back and forth along that same line.

* Transverse waves are waves where the particles of the medium vibrate perpendicular to the direction the wave travels. Think of a wave on a string. The string moves up and down (perpendicular to the direction the wave travels), but the wave itself moves along the string.

Examples of longitudinal waves:

* Sound waves: Sound travels through air, water, or solids as compressions and rarefactions.

* Seismic P-waves: These are the fastest type of seismic wave and travel through the Earth's interior as compressions and rarefactions.

Let me know if you have any other questions!