The neural circuits involved in action control and in the first-person experience of emotions are also active when witnessing the same actions and emotions of others. This revolutionary discovery gave rise to many theories and claims about the above functional mechanism, called «Mirror Neuron System» (MNS). According to a widely accepted idea, the MNS forms the basis of empathy and allows the direct recognition and understanding of other people's emotions. We compared these theories with empirical evidence, in order to define the most important concepts and identify potential inaccuracies, misunderstandings and generalizations. We then tried to understand what can be said about the exact role played by the MNS in terms of empathy, recognition and understanding of emotions.