The dynamics of soliton and quasisoliton solutions of cubic third order
nonlinear Schr\"{o}dinger equation is studied. The regular solitons exist due
to a balance between the nonlinear terms and (linear) third order dispersion;
they are not important at small α3 (α3 is the coefficient in
the third derivative term) and vanish at α3→0. The most essential,
at small α3, is a quasisoliton emitting resonant radiation (resonantly
radiating soliton). Its relationship with the other (steady) quasisoliton,
called embedded soliton, is studied analytically and in numerical experiments.
It is demonstrated that the resonantly radiating solitons emerge in the course
of nonlinear evolution, which shows their physical significance