Compression occurs when particles in a medium are pushed close together, resulting in an area with high pressure and density.
Rarefaction happens when particles spread apart in a medium, resulting in an area with low pressure and density.
Longitudinal Wave: A longitudinal wave consists of compressions and rarefactions moving parallel to each other.
Sound Wave: Sound waves are examples of longitudinal waves that require particles to compress and rarefy in order to transmit sound energy.