In the early 1970s, the earliest instances of word-of-mouth marketing occurred when customers indicated interest in a company's products or services during casual discussions. Client interactions that surpass their expectations typically generate word-of-mouth promotion for businesses. Due to the increasing adoption of new technologies, electronic word-of-mouth has enabled people to engage with the global market via Internet of Things (IoT) based comments and opinions. In addition, the Covid-19 pandemic has led to an increase in eWOM use. In this paper, eWOM-influencing concepts and factors are investigated. In addition to discussing the effects of eWOM, the effects of COVID-19 on eWOM in the hotel and tourism industries are also examined. This research studies the causes and effects of eWOM.