Here's why:

* Mechanical waves require a medium (matter) to travel. The particles in the medium vibrate or oscillate, transferring energy from one particle to the next. This vibration propagates through the medium as a wave.

* Transverse waves are mechanical waves where the particles vibrate perpendicular to the direction the wave travels (like a wave on a string).

* Compressional waves (also called longitudinal waves) are mechanical waves where the particles vibrate parallel to the direction the wave travels (like sound waves).

Examples of mechanical waves:

* Sound waves: These are compressional waves that travel through air, water, or solids.

* Water waves: These are a combination of transverse and longitudinal waves.

* Seismic waves: These are waves that travel through the Earth's crust, mantle, and core.

Important note: Electromagnetic waves, like light, do not require a medium and can travel through a vacuum.