Typically, there are two methods of achieving open access: self-archiving in an institutional repository (“Green OA”) and journal publishing (“Gold OA”). Open access relates to the free availability of research literature and does not determine whether an article is peer-reviewed. Peer-review is conducted by a journal's editorial board, not a repository.
“Green OA” occurs when authors make copies of their work freely available in an institutional repository or online archive. Example repositories include arXiv, PubMed, and Pepperdine Digital Commons. Self-archived works may be preprints (submitted for peer-review), postprints (post peer-review), or the final article (formatted for publication).
Scholarly articles and journals that are not open access require costly subscription or article fees, which the library pays to provide users access. While open access provides free access to researchers, publishing costs are often shifted to authors in "Gold OA". Less than 50% of open access journals charge fees (sometimes referred to as article processing costs or APCs), which may be covered by sponsorships, authors’ institutions, or grants.
A few defining statements on Open Access:
Budapest Open Access Initiative (2002)
Bethesda Statement on Open Access Publishing (2003)
Berlin Declaration on Open Access to Knowledge in the Sciences and Humanities (2003)
Addendum - attached to publication or copyright transfer agreements requesting additional author rights beyond those already granted by the publisher.
APC - Article processing cost, also article publication fee. "A fee charged by some OA journals when accepting an article for publication in order to cover costs of production. While the bill goes to the author, the fee is usually paid by the author's funder or employer, not by the author out of pocket." - Suber, Open Access (2013), 176.
Creative Commons - a nonprofit organization that creates licenses under which works are distributed with reuse permissions granted upfront.
Gold OA - OA published by journals
Green OA – OA published by repositories, self-archiving
Hybrid OA - article-level OA in traditional non-OA subscription access journals
Postprint - also known as the author's final version, this version incorporates all changes from peer review,
but it has not yet been copyedited and formatted for publication.
Preprint - version of a scholarly work submitted for peer review including only the original work of the author(s).
Repository - An online database of OA works. Repositories don’t perform peer-review, but they may host articles that have been peer-reviewed elsewhere. They frequently host preprints that have yet to be peer-reviewed, electronic theses and dissertations, books or book chapters, datasets, and digitized print works from the institution’s library. Institutional repositories aim to host the research output of an institution. - Peter Suber, Open Access (2013), 176.