  We study large N dualities for a general class of N=1 theories realized on
type IIB D5 branes wrapping 2-cycles of local Calabi-Yau threefolds or as
effective field theories on D4 branes in type IIA brane configurations. We
completely solve the issue of the classical moduli space for N=2, U(N_1)x ... x
U(N_n) theories deformed by a general superpotential for the adjoint and
bifundamental fields. The N=1 geometries in type IIB and its T-dual brane
configurations are presented and they agree with the field theory analysis. We
investigate the geometric transitions in the ten dimensional theories as well
as in M-theory. Strong coupling effects in field theory are analyzed in the
deformed geometry with fluxes. Gluino condensations are identified the
normalizable deformation parameters while the vacuum expectation values of the
bifundamental fields are with the non-normalizable ones. By lifting to M
theory, we get a transition from finite coverings of non-hyperelliptic curves
to non-hyperelliptic curves. We also discuss orientifold theories, Seiberg
dualities and mirror symmetries.
