Here's why:
* Longitudinal waves involve the particles of the medium vibrating parallel to the direction the wave travels. Imagine a spring: if you push one end, the compression travels down the spring as individual coils move back and forth in the same direction the compression travels.
* Transverse waves involve the particles of the medium vibrating perpendicular to the direction the wave travels. Think of a wave on a rope: the rope moves up and down (perpendicular), while the wave travels horizontally.
Examples of longitudinal waves include:
* Sound waves in air, water, and solids.
* Seismic P-waves (primary waves) which travel through the Earth's interior.
