The purpose of this paper is to present the concept of one of the most effective marketing tools: Traditional Word-of-Mouth (WOM) and Electronic Word-of-Mouth (eWOM). First, the paper mentioned the different definitions for both of them and their elements and features. Why have they become one of the essential marketing tools? Then the similarities and differences between WOM and eWOM have been explained. After that, the paper summarized the factors that led to the transfer and the digitized of Word-of-Mouth. In addition, the paper mentioned the impact of both Traditional Word-of-Mouth (WOM) and Electronic Word-of-Mouth (eWOM).