  We discuss quantum and classical aspects of two-photon interference in light
transmission through disordered media. We show that disorder is the main factor
that suppresses the interference, whatever the quantum state of the incident
light. Secondarily, the two-photon interference is affected by the quantum
nature of light (i.e., the well-defined number of photons in the two-photon
entangled and Fock states as compared to the coherent state). And finally,
entanglement is a resource that allows to prepare two-photon states with
special symmetries with respect to the interchange of the photons and, in
particular, the states with bosonic and fermionic symmetries. The two-photon
interference is more robust for the latter states and its sign can be inverted
for the fermionic state.
