P-waves, or primary waves, are a type of seismic wave generated by earthquakes. They are the fastest seismic waves, traveling through solids, liquids, and gases. P-waves compress and expand the material they move through, similar to how sound waves travel through air. This ability to move through different states of matter makes them crucial for understanding the Earth's internal structure. When an earthquake occurs, P-waves are the first to be detected by seismographs, allowing scientists to quickly assess the event's location and magnitude. Their speed and behavior provide valuable information about the composition of the Earth's layers, including the mantle and core.