Chapter one introduced distance learning definitions and concepts as applied to education and training. An important consideration when choosing among DL technologies is the potential effect of DL technology use on the learning experience. This chapter provides a discussion of key learning variables in the learning process and outcome. These variables characterize and differentiate the DL technologies and are used in the course evaluation and media selection process. After the learning variables are presented in this chapter, the instructional technologies are discussed and evaluated in chapter three. Finally, readers will find the details of the screening process for distance learning described in depth in chapter four.