Affective polarization has recently become one of the phenomena of greatest interest to social researchers. The large number of papers on this concept requires a systematic review to organize its main explanatory theories. In the following, we analyse the distinctive dimensions of affective polarization, a political polarization with non-political effects, and the hypotheses that help us to understand its emergence, from the perspective of the masses, the elites and the media ecosystem. In particular, we are confronted with the possibility that ideological radicalization is at the origin of this affective polarization or that, on the contrary, without being so far apart in ideas, it is the constitution of political identities as social identities that causes a perceptual sense of false polarization that induces greater animosity between the supporters of the conflicting groups.