The use of social networks has proliferated in recent years. Although it is a very recent phenomenon, there are more and more types of networks used for different purposes. This is a review of the results of different researches carried out around this social phenomenon in Spain. To introduce the context this study retrieves a historical retrospective from the origins of social networks in the US at the end of the last century until today. The analysis begins with the results of the IAB Spain research " Situation on Social Networks 2019". The main conclusions are compared with those obtained from the research on social networks carried out by Publicis Media to understand consumer habits in this environment " Discovering Social Networks: Map of Consumption and use in Spain 2019". This followed by a comparative analysis of the results of both research, focusing on Social Network trends and an in-depth study on the most popular social platforms in Spain: Youtube, Facebook, Instagram, WhatsApp, and Twitter. Although social networks are perceived as platforms for young people, there is a very high consumption in the profiles called "perennials", which respond to a behavioral or attitudinal profile rather than a sociodemographic one. To conclude this reflection there is a focus on advertising in Social Networks, analyzing the perception of users and the behavior of brands as recorded in the " VII Observatory of Brands in Social Networks" published in 2019 by IAB Spain.