Open Access is a movement responding to the high cost of scholarship and science. The Public Library of Science (PLoS) explains Open Access this way —
“Open Access (OA) stands for unrestricted access and unrestricted reuse. Here’s why that matters.
“Most publishers own the rights to the articles in their journals. Anyone who wants to read the articles must pay to access them. Anyone who wants to use the articles in any way must obtain permission from the publisher and is often required to pay an additional fee.
“Although many researchers can access the journals they need via their institution and think that their access is free, in reality it is not. The institution has often been involved in lengthy negotiations around the price of their site license and re-use of this content is limited.
“Paying for access to content makes sense in the world of print publishing, where providing content to each new reader requires the production of an additional copy, but online it makes much less sense to charge for content when it is possible to provide access to all readers anywhere in the world.”
Jorge Cham at “Piled Higher and Deeper” (PHD) Comics, along with Nick Shockey and Jonathan Eisen, provide this animated explanation of Open Access.