Heavy Exotic Mesons

I will introduce the topic of heavy multiquark states, with special attention to the current theoretical and experimental status. I will first review the available experimental information and then discuss them in the context of the two most likely interpretations of these states: the compact tetraquark and the loosely bound meson molecule. In particular, I will focus on those features of the two interpretations that are universal and do not rely on their particular phenomenological realizations, in order to isolate a set of observables that can discriminate between the two.