Over the years, interest in studying the evolution of social dynamics over graphs has greatly increased: different models and types of dynamics have been proposed to analyze how the nodes of a graph interact. These nodes can be conceivable as human individuals interacting, animals, cells or any other element whose behavior can be understood if placed inside a network and analysed through some sort of dynamics on this network. This thesis aims at reviewing many of the models proposed to describe opinion formation under some social influence, hence analysing a recent model of social influence in which the real opinions are concealed to the other nodes of the network and only seen through a filter, a quantizer.