"Open Access is the needed modern update for the communication of research that fully utilizes the Internet for what it was originally built to do—accelerate research." -SPARC*
Open Access (OA) refers to all electronic resources that are made widely available on the internet without licensing and copyright restrictions. Open Access resources can include articles, journals, books, conference proceedings, theses, videos, music, etc.
Open Access has become widely popular in scholarly research and communication as the prices of academic resources have grown significantly this past decade and academic libraries budgets have not risen to meet these new expenses.
Credit: SPARC* (https://sparcopen.org/open-access/)
Green OA: This type of Open Access includes peer-reviewed articles that are in their pre- or post- print versions. Authors of these articles will deposit their final version of an article to be published in an established journal in an Open Access repository/depository. The copyright of the version deposited in the OA repository will remain with the author. Often an embargo (a set period of time where the article will only be available by purchase before going OA) will be established for these articles by the author to meet publisher regulations.
Gold OA: This type of Open Access includes articles published through a traditional journal publisher. The Author Processing Charges (APC) are fees paid by the author, grants, sponsoring societies, or advertisements to publish the article as Open Access. There are no embargoes placed on these articles once published. Gold OA journals are often Open Access only or are considered a hybrid journal.
Hybrid OA: This type of Open Access is often referred to as "Paid Open Access." Hybrid journals are subscription based but will include individual OA articles. These journals are published through subscription fees and Author Processing Charges (APC).
Credit: Verminski, A., & Blanchat, M. (2017). ALA fundamental series: Fundamentals of electronic resources management. American Library Association.
More people can read the results of scholarly research, including those who would otherwise not be able to access that information because they cannot afford the subscription to an expensive journal, for example.
New ideas can be dispersed more rapidly and widely, which in turn triggers new research studies; it serves as an impetus for knowledge.
Scientific research shows that publishing in open access, because of the worldwide visibility without barriers, demonstrably leads to more citations and more impact.
Businesses also have broad access to the most recent scientific ideas, which they can then build upon. Open access contributes to the knowledge economy and provides an economic boost.
Since open access also implies wider reuse, recent knowledge can be put to immediate use in teaching as "open educational resource".
Credit: open access.nl (https://www.openaccess.nl/en/what-is-open-access/pros-and-cons)
"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."
From Peter Suber's Very brief introduction to Open Access.
For "a concise introduction to the basics of open access, describing what it is (and isn't) and showing that it is easy, fast, inexpensive, legal, and beneficial," please see Peter Suber's Open Access from MIT Press here.