In the Standard Model, flavour changing neutral current processes such as b->s transitions do not occur at tree level. The suppression of these decays in the SM makes them effective probes of beyond the Standard Model physics. While so far most of the data on rare B-decyas have been in agreement with the predictions of the SM, in the past few years several tensions have been observed which offer some of the most promising signs of NP. In this talk we will present an overview of the theoretical framework for these processes. We then address the so-called B-physics anomalies and consider the different sources which could explain the tensions.