Since ten years experiments have been observing a host of exotic states decaying into heavy quarkonia. The interpretation of most of them still remains uncertain and, in some cases, controversial, notwithstanding a considerable progress has been made on the quality of the experimental information available and a number of ideas and models have been put forward to explain the observations. In this talk we will expose the state-of-the-art of exotic spectroscopy, and will review the most promising theoretical interpretations, in particular we will discuss the nature of Zc(3900), a charged charmonium-like state recently discovered at BES and Belle. Finally, we will propose a new mechanism to explain the prompt X(3872) production cross section at hadron colliders.