Tutoring earth science, p-waves and s-waves might arise. The tutor gives quick definitions.
compression waves from a seismic event (eg earthquake). These waves cause the earth to vibrate in their direction of travel. Imagine how a shock-absorber in a car moves: that models a p-wave as it reaches and passes each point.
transverse waves from a seismic event: they are similar to water waves you see in a pool.
P-waves are sometimes called primary waves, since they arrive at a distant location before the S-waves (aka secondary waves). In fact, primary waves travel about twice as fast as secondary.
Trefil, James, Ph.D., et al. The Changing Earth. Evanston: McDougall Littell, 2005.Oracle Tutoring by Jack and Diane, Campbell River, BC.