**Stanislav Dubniˇcka 1, Anna Zuzana Dubniˇcková 2, Mikhail A. Ivanov <sup>3</sup> and Andrej Liptaj 1,\***


Received: 6 May 2020; Accepted: 26 May 2020; Published: 29 May 2020

**Abstract:** We review the existing results on the exotic XYZ states and their decays obtained within the confined covariant quark model. This dynamical approach is based on a non-local Lagrangian of hadrons with quarks, has built-in quark confinement, and is suited well for the description of different multiquark states, including the four quark ones. We focus our analysis on the various decay modes of five exotic states, *X*(3872), *Zc*(3900), *Y*(4260), *Zb*(10610), and *Z*- *<sup>b</sup>*(10650), aiming to clarify their internal quark structures. By considering mostly branching fractions and decay widths using the molecular-type or the tetraquark-type interpolating currents, conclusions about the nature of these particles are drawn: the molecular structure is favored for *Zc*(3900), *Zb*(10610), and *Z*- *<sup>b</sup>*(10650) and the tetraquark for *X*(3872) and *Y*(4260).

**Keywords:** exotic states; confined covariant quark model; strong and radiative decays
