In this paper, we introduce a type of path-dependent quasilinear (parabolic)
partial differential equations in which the (continuous) paths on an interval
[0,t] becomes the basic variables in the place of classical variables
(t,x). This new type of PDE are formulated through a classical backward
stochastic differential equation (BSDEs, for short) in which the terminal
values and the generators are allowed to be general functions of Brownian
paths. In this way we have established a new type of nonlinear Feynman-Kac
formula for a general non-Markovian BSDE. Some main properties of regularities
for this new PDE was obtained