Here's the breakdown:

* Mechanical Waves: These are the waves we usually think of, like sound waves and water waves. They require a medium (like air, water, or a solid) to travel through. The particles in the medium vibrate or oscillate, transferring energy from one particle to the next. This creates the wave-like motion.

* Electromagnetic Waves: These are a different type of wave and don't require a medium. Instead, they are made up of oscillating electric and magnetic fields that are perpendicular to each other. Think of light waves, radio waves, microwaves, and X-rays. They can travel through the vacuum of space because they don't rely on physical particles to transfer energy.

So, while electromagnetic waves can travel through a vacuum, mechanical waves need a medium to propagate.