The main goal of the issue is to provide authoritative reviews on selected topics discussed in the field in the last few years. Nevertheless many articles contain significant original research. The opening section of the issue is dedicated to foundational aspects of quantum mechanics. The second section deals with diverse quantum information insights into the analysis of quantum resources (like entanglement and quantum discord). Many of the concepts presented in the first part of the issue are applied to spin systems. The last sections of the issue is focused on the dynamics of quantum discord in open systems.