Pdepe solver - how does it work?

I have 2 questions about the theory behind the pdepe solver.

The spatial discretization is based on a piecewise nonlinear Galerkin/Petrov-Galerkin method. What is the order of the interpolating polynomials?

This discretization yields a system of linear algebraic equations. What is the iterative method employed by the pdepe function to solve this system?

[Alessandro Ferreri]

I found out that for m = 0, the polynomial is linear.

Moreover, the linear equation resulting from the implicit time integration method (Numerical differentiation formulae) are solved by means of a Lower Upper (LU) decomposition method and backward substitution.

[feynman feynman]

good question

[Torsten]

Which question ? @Alessandro Ferreri answered them in his comment.