The talk will be a very basic introduction of open quantum systems, where we will see why CPTP maps are important and how we can characterize them. We will talk about "superoperators" induced by quantum operations, the Choi-Kraus theorem, and Lindbladians. The ideal public will consist of master and PhD students, together with researchers who have never heard about these topics. Of course, experts are also more than welcome; they will have the pleasure of understanding everything and help me explain things even better.