noindent Neutrino Oscillations. \ par In the second lecture we will construct the simplest theoretical framework, the so-called standard three neutrino paradigm, that enables one to understand the results of the neutrino oscillation experiments. We will discuss neutrino oscillations in vacuum and in matter. In view of this theoretical framework we will revisit the experimental results and discuss the status today of the standard paradigm. We will consider simple extensions of the three neutrino picture that can be evoked to explain some of the anomalies in neutrino data.