Social networks have become an indispensable part of human life, and we use them automatically, so few people think about the advantages and disadvantages that social networks bring. This final paper primarily investigates how social networks can affect people's mental health and their interpersonal relationships. Knowledge of social networks is important for further research; therefore, in the first part of the paper, social networks, their way of working, and the purpose of their use will be described in detail. Also, the beginning of their creation will be investigated, followed by a description of larger platforms through Facebook, Instagram, TikTok, and X. In the central part, the focus of the work will be on mental illnesses (depression, anxiety, and self-esteem) and the analysis of potential connections with social networks. The influence of the use of platforms on children and adolescents will be highlighted in particular. Furthermore, interpersonal relationships will be divided into family relationships, friendships, and love relationships, and it will be found how social networks affect the relationships themselves. Also, the replacement of real communication with virtual communication and how it affects our behavior and the maintenance of relationships will be considered. The sequel will show the impact of the pandemic on social networks, mental health, and interpersonal relationships. In the end, some tips will be given on how to maintain a positive mood and interpersonal relationships while using social networks.