A wave is some sort of physical disturbance that carries energy from one place to another without carrying matter. Sound and light are two very common waves we encounter that have some similarities and some important differences. One important aspect of a type of wave is how the disturbance moves relative to the direction the wave is traveling. In this silent animation a hand compresses a slinky to start a compression or longitudinal wave, a type of wave where the disturbance lines up with the direction the wave travels.
Learn more at Animations for Physics and Astronomy.