Open access resources refer to information and research outputs distributed online and free of cost or other barriers, including copyright. They may be public domain, such as resources put out by governments; preprint articles awaiting peer review in a university repository before journal publication; or research such as data, software, or Creative Commons licensed white papers and technical reports to promote dissemination and reuse. (Adapted from Wikipedia, Open Access article).
adapted from Carnegie Mellon Information Systems LibGuide