This year's theme, It Matters How We Open Knowledge: Building Structural Equity, is based on the UNESCO Recommendation on Open Science, in which the member countries of UNESCO will seek "to define shared values and principles for Open Science, and identify concrete measures on Open Access and Open Data, with proposals to bring citizens closer to science and commitments to facilitate the production and dissemination of scientific knowledge around the world." The Recommendation is currently in draft form, to be presented at the UNESCO General Conference in November 2021.
"Open-access (OA) literature is digital, online, free of charge, and free of most copyright and licensing restrictions. What makes it possible is the internet and the consent of the author or copyright-holder." Peer-reviewed scholarly research is made openly available through the use of permissive licenses agreed to by the author and publisher, sometimes following the author's payment of an "article processing charge" (APC) to the publisher, though many OA journals publish without an author charge. Scholars are sometimes bound by their funding agreement to make their publications open, but many scholars decide to publish their work open access to increase readership and citation of their work.
Creative Commons licenses were created as a way to give authors the ability to make their works accessible online beyond the restrictions of traditional copyright. Authors can assign a range of licenses depending on how they want their works to be accessed and/or reused.