Open Access Publishing

Open access (OA) means free access to information and unrestricted use of electronic resources for everyone. Any kind of digital content can be OA, from texts and data to software, audio, video, and multi-media. While most of these are related to text only, a growing number are integrating text with images, data, and executable code. 

Ideally, a publication is considered in Open access if:

• its content is universally and freely accessible, at no cost to the reader, via the Internet or otherwise;
• the author or copyright owner irrevocably grants to all users, for an unlimited period, the right to use, copy, or distribute the article, on condition that proper attribution is given;
• it is deposited, immediately, in full and in a suitable electronic form, in at least one widely and internationally recognized open access repository committed to open access.

From the United Nations Educational, Scientific, and Cultural Organization (UNESCO) 
https://en.unesco.org/open-access/what-open-access

HowOpenIsIt? The Open Access Spectrum Guide, issued by PLOS, SPARC, and OASPA https://sparcopen.org/our-work/howopenisit/

Except noted works attributed.