A P-wave is a type of seismic wave that can travel through a continuum. A P-wave can also be referred to as a compressional wave, a primary wave or a pressure wave.
P-waves can be produced by earthquakes. During an earthquake, P-waves tend to shake the ground in alternating directions, the same direction and the opposite direction of the wave's movement. A P-wave is the first wave to be recorded by a seismograph during an earthquake. All body waves, primary and secondary, occur and travel within the core of the Earth. These waves are used to map the structure of the planet's interior.