Sound is a mechanical vibration
Sound is a regular mechanical vibration that travels through matter as a waveform. It consists of longitudinal or compression waves in matter.
Travels through matter
Although it is commonly associated in air, sound will readily travel through many materials, such as water and steel. Some insulating materials absorb much of the sound waves, preventing the waves from penetrating the material.
Sound waves are different than light waves
Light and radio waves are electromagnetic waves. They are completely different than sound, which is vibration of matter. Electromagnetic waves are related to electrical and magnetic fields and readily travel through space.
Sound is a longitudinal wave
The rapid back-and-forth vibration of an object creates the longitudinal or compression waves of sound. Longitudinal waves are waves that oscillate in the same path that the sound wave is moving. This is different than the up and down or transverse motion of a water wave.