Open access is a broad international movement that seeks to grant free and open online access to academic information, such as publications and data.
A publication is defined 'open access' when there are no financial, legal or technical barriers to accessing it - that is to say when anyone can read, download, copy, distribute, print, search for and search within the information, or use it in education or in any other way within the legal agreements.
Source: https://www.openaccess.nl/en/what-is-open-access
Image Source: https://www.depts.ttu.edu/library/oer/whatisoer.php
Open Educational Resources (OER) are teaching and learning materials that you may freely use and reuse at no cost, and without needing to ask permission. Unlike copyrighted resources, OER have been authored or created by an individual or organization that chooses to retain few, if any, ownership rights.
Source: https://oercommons.org/about
Image Source: https://uow.libguides.com/open-research/oer