In physics, a phonon is a quantized lattice vibration. The word quantized is used in physics to mean that only certain values of something are allowed. Something that is quantized can be thought of as stairs; you can only move from step to step and you can't stand in between steps. Something that is not quantized can be thought of as a ramp or smooth incline; you can move any distance up or down. A lattice is the repeating or periodic structure of a crystal. A crystal is made up of atoms or molecules in a certain pattern. The points on the pattern at which the atoms or molecules are located is the lattice. Solids, liquids, and gases can all experience vibrations. A vibration being quantized means that only certain frequencies of vibrations are allowed.