Open Access is commonly understood to mean "free, immediate, online availability of research articles, coupled with the rights to use these articles fully in the digital environment." (SPARC, 2013)
The list below includes the most common variations employed by publishers.
Public Library of Science (PLOS) is a good place to start learning about Open Access, its value to scholarship and ways to advocate for it.
Open Access Models
Total Open Access: All the articles in a journal are free and accessible on the Internet. Article processing fees are usually required to cover the costs of peer-review and online publication and are paid by the author, the author's institution, or the author's research grant. Many open access journals offer institutional memberships where, based on the level of membership, article processing fees are either reduced or waived.
Delayed Open Access: Journal articles are freely available after a period of paid access, anywhere from 6 to 12 months, expires.
Short-term Open Access: Free access to journal articles is provided for a short time after publication, after which access is only available to subscribers.
Selected Open Access: Selected journal articles are freely available, while the remaining articles are accessible by subscription.
Hybrid Open Access: Authors are given the option to pay a publication fee to make their article freely available immediately on publication.
Partial Open Access: The primary research articles of a journal are made freely available, but access to other value-added content such as editorials and review articles requires a subscription.