I will talk about my work during my doctoral studies on neutrino oscillation phenomenology and new physics thereof, which I undertook in Karlsruhe, Germany, under the supervision of Thomas Schwetz. I will give an introduction to neutrino oscillations to the uninitiated, and then an overview of the current three-neutrino global fit of oscillation parameters. Then I will talk about evidence for a fourth light sterile neutrino, particularly in the context of possible signals from Neutrino-4 and BEST. Then I will talk about constraining the neutrino dipole portal, where a SM neutrino has a transition magnetic moment with a heavy fourth neutrino (a.k.a. heavy neutral lepton). I studies possible new signals at DUNE, a neutrino-oscillation experiment currently being built.