Reference management software, citation management software, can be a great help in collecting and evaluating literature. You can record ideas and quotations, evaluate PDF documents or simply create bibliographies. These functions are particularly useful when writing theses (Bachelor's, Master's or doctoral theses).
For Windows users we recommend Citavi. (There is a Passau University license!)
For Mac or Linux users we recommend the open source software Zotero. (https://www.zotero.org/)
For a detailed comparison of reference management software we recommend this list on Wikipedia.