For the purposes of this discussion, though, directed stress is more important to me. Directed stress is what deforms rock, and directed stress is usually a result of tectonic forces, so it's important for earthquakes. This stretches rocks out. Compressional Take your bubble gum, stick it between your fingers, and squeeze. You've just applied compressional stress to your gum.
Compressional stress squishes things.
If you apply force in opposite directions on the opposite ends of a rock layer, you may shear the rock. As you do that, the cards will slide past each other in response to the shear stress you've put them under. See Figure 10.6 in your book for a discussion of tensional, compressional, and shear directed stresses. If you apply stress to rocks, they will deform, or change shape. The two major ways rocks deform are to bend or break.