A P Wave, or primary wave, is a type of seismic wave generated by earthquakes. It is the fastest seismic wave, traveling through solids, liquids, and gases. P Waves compress and expand the material they move through, creating a back-and-forth motion. This characteristic allows them to be detected first by seismographs during an earthquake. In the context of the Earth's interior, P Waves provide valuable information about the structure of the planet. They can travel through the Earth's mantle and outer core, helping scientists understand the composition and behavior of these layers. Their speed and path reveal important details about the Earth's geology.