The material through which a wave travels is called the medium.
When we talk about waves, we are referring to disturbances that transfer energy from one point to another. For example, sound waves require a medium such as air, water, or a solid substance to propagate. When a wave travels through a medium, it causes the particles of that medium to oscillate around their equilibrium positions, allowing the wave to carry energy through the medium. Different types of waves can travel through different media, with some waves like electromagnetic waves being capable of traveling through a vacuum where no medium is present.