Open access (OA) refers to unrestricted online access to articles published in scholarly publications. Types of open access publications available online include: articles books and book chapters conference papers theses working papers data images

"By 'open access' ... we mean its free availability on the public internet, permitting any users to read, download, copy, distribute, print, search or link to the full text of these articles, crawl them for indexing, pass them as data to software or use them for any other lawful purpose…" The Budapest Open Access Initiative

The basic concepts behind OA publishing and why it is so important, © Jorge Cham PhD Comics