  Tetraquark properties are examined in the limit of large $N_c$ of color in
QCD. The qualitative differences between molecular and compact tetraquarks are
outlined. Consequences of the possible existence of compact tetraquarks are
analyzed and shown to lead to upper bounds in the $N_c$-behavior of their decay
widths. Open questions on theoretical grounds, related to the dynamics of
systems composed of two quarks and two antiquarks, are addressed.
