  We discuss a description of chiral symmetry breaking in the light-front (LF)
formalism. Based on careful analyses of several models, we give clear answers
to the following three fundamental questions: (i) What is the difference
between the LF chiral transformation and the ordinary chiral transformation?
(ii) How does a gap equation for the chiral condensate emerge? (iii) What is
the consequence of the coexistence of a nonzero chiral condensate and the
trivial Fock vacuum? The answer to Question (i) is given through a classical
analysis of each model. Question (ii) is answered based on our recognition of
the importance of characteristic constraints, such as the zero-mode and
fermionic constraints. Question (iii) is intimately related to another
important problem, reconciliation of the nonzero chiral condensate and the
invariance of the vacuum under the LF chiral transformation. This and Question
(iii) are understood in terms of the modified chiral transformation laws of the
dependent variables. The characteristic ways in which the chiral symmetry
breaking is realized are that the chiral charge is no longer conserved and that
the transformation of the scalar and pseudoscalar fields is modified. We also
discuss other outcomes, such as the light-cone wave function of the
pseudoscalar meson in the Nambu-Jona-Lasinio model.
