Here's the breakdown:

* Mechanical waves require a medium to travel. This is because they are caused by the vibration of particles within a medium. Examples include sound waves (which travel through air, water, or solids), water waves, and seismic waves.

* Electromagnetic waves do not need a medium. These waves are made up of oscillating electric and magnetic fields that can travel through a vacuum. Examples include light, radio waves, microwaves, X-rays, and gamma rays.

Therefore, while some waves require a medium to propagate, others, such as electromagnetic waves, can travel through the vacuum of space.