  We discuss how to understand the dynamical process of Kuznetsov-Ma breather,
based on some basic physical mechanisms. It is shown that dynamical process of
Kuznetsov-Ma breather involves at least two distinctive mechanisms:
modulational instability, and the interference effects between a bright soliton
and a plane wave background. Our analysis indicates that modulational
instability plays dominant roles in mechanism of Kuznetsov-Ma breather
admitting weak perturbations, and the interference effect plays dominant role
for the Kuznetsov-Ma breather admitting strong perturbations. For intermediate
cases, the two mechanisms are both involved greatly. These characters provide a
possible way to understand the evolution of strong perturbations on a plane
wave background.
