Open Access refers to journals and scholarly information available digitally for free on the Internet with no licensing or copyright restrictions. There are various levels of open access available. Some journal articles are available free to anyone at the time of publication. Publishers may have the option to restrict access to some journal articles for a few months to a few years before allow the article to become open and posted to the web without restriction. Fore more complete information and definitions on open access see open access advocate, Dr. Peter Suber's Very Brief Introduction to Open Access.
All of the links on this tab were taken from Susan Wortman's guide at the University of Michigan: https://guides.lib.umich.edu/stayinformed