This chapter is organized as follows. Section 2.1 explicates the theoretical background of eWOM in marketing and the computer-mediated environment. Section 2.2 describes the history of the origination of eWOM and section 2.3 describes the development of eWOM. In Section 2.4, we discuss the various types of eWOM and provide a definition. Finally, Section 2.5 highlights the motives of eWOM in marketing by addressing the benefits that both senders and receivers may gain from them.