This chapter sets the scene for the discussion, presenting the MHD equations and their basic properties before turning to a discussion of the basic ideas of wave propagation. A variety of plasmas are also briefly reviewed with most attention devoted to the solar atmosphere and its observed features. Coronal loops and sunspots are given some attention.
The process of linearization of equations is described. Also, the two fundamental speeds that arise, the sound speed and Alfven speed, are defined and evaluated for illustrative purposes. The concepts of phase speed and group velocity are introduced.