This talks contains a short introduction to Chiral Perturbation Theory and
the existing calculations to two-loop order in the mesonic sector. I include a
discussion on which quantities the expansion can be organized in. The present
best values of the Low-Energy-Constants as determined from continuum physics
are given as well as the assumptions underlying the fits to experimental data.
I present plots of masses, decay constants and f+β(0) in Kβ3β as a
function of quark or meson masses. The talk ends with a list of things for
which it would be extremely useful to have good results from lattice QCD
calculations.Comment: 15 pages, plenary talk at T he XXV International Symposium on Lattice
Field Theory, July 30 - August 4 2007, Regensburg, Germany. v2: some
clarifying statements adde