New light-quark spectral function from tau decays: implications to QCD and g-2 of the muon

QCD remains one of the most challenging ingredients for precision Standard Model tests. In this colloquium I will outline some of the challenges involved in the use of QCD at relatively low energies and how a new tau-decay-based vector-isovector spectral
function can be used in order to constrain theory and generate new data-driven predictions. In this context, I will discuss the
determination of the strong coupling and tests of asymptotic freedom, the comparison between experimental and lattice-QCD data, and a detailed scrutiny of the Standard Model evaluation of the muon anomalous magnetic moment.