This review is the first attempt to systematize the results on shock waves in granular gases. We present experimental and computational evidences of shock and expansion waves propagating within granular gases. The analysis of model flows with shock and expansion waves shows that even smallest kinetic energy dissipations crucially affects such flows. We discuss the role of these waves for the fluidization of a granular flow by an obstacle, and of a granular layer by a vibrating vessel. The efficacy of hydrodynamic models for the description of shock-expansion wave flows is demonstrated. We also show that these waves play the dominant role in vibrofluidization of highly dissipative granular layers as frequently found in nature and engineering applications.