Sound waves are longitudinal. Describe a longitudinal sound wave.

There are two types of wave: longitudinal and transverse. It's really important to learn their properties as this is a very common question. The main thing to remember is longitudinal waves have oscillations parallel to the direction of energy transfer. The longitudinal wave consists of compressions (where the particles are compressed!) and rarefractions (where they are spread out). It can be imagined to be like pushing a slinky back and forth! If this question were to ask about transverse, these oscillations move perpendicular to the direction of every transfer.