  Diffractive phenomena constitute a large fraction of interactions occurring
in pp collisions at LHC. Because of the non-perturbative nature, their present
understanding is still relatively poor and uncertain. One of the methods to
study these processes is forward proton tagging. I will discuss the mechanism
of diffractive processes, recent results, and potential implications. The
proton tagging method can also be used for measurements of photon-induced
processes, in particular, the photon-photon interactions. I will present the
physics behind these processes, the experimental status and the lessons we can
learn for the strong interactions and for the electroweak sector.
