We present the legal framework for knowledge and data licensing with the focus on different kinds of free/libre licenses. The special attention is given to the Creative Commons and META-SHARE licenses since those define some concepts which are easy to understand and universally applicable to other licenses. We cover the most important licenses for documents and works of art by going through a several real-world examples. In the end, we give a short overview of the specificities of the software licensing along with the most commonly used ones like BSD and GNU licenses.