Abstract: Once thought to be a peculiarity exhibited by a minority of stars, stellar oscillations are now regarded as the rule rather than the exception. Across the whole Hertzsprung-Russell diagram, we see evidence of the periodic photospheric motions that are the hallmark of the excitation of one or more oscillation modes. In this review talk, I'll discuss the wave properties of these modes; explore the various mechanisms for their excitation; explain how they can be used to probe the internal structure of stars, through the discipline of asteroseismology; and, consider how oscillation modes might alter this internal structure.