Mechanical waves are classified according to the direction of the wave's motion relative to the direction of the particles' vibration. Here's how it breaks down:

* Transverse Waves: The particles vibrate perpendicular to the direction the wave travels. Think of a wave on a string or light waves.

* Longitudinal Waves: The particles vibrate parallel to the direction the wave travels. Sound waves are a classic example.

Let me know if you'd like to learn more about either type of wave!