Pete Suber, Director of the Harvard Open Access Project, defines Open Access (OA) literature as:
"digital, online, free of charge, and free of most copyright and licensing restrictions. What makes it possible is the internet and the consent of the author or copyright-holder...OA is entirely compatible with peer review, and all the major OA initiatives for scientific and scholarly literature insist on its importance. Just as authors of journal articles donate their labor, so do most journal editors and referees participating in peer review."
However, some open access publishers are NOT legitimate (“Predatory Publishers”) and exist for the sole purpose of profit (from author fees) not the dissemination of high-quality research findings
Gold OA: Means publishing with publishers that automatically and immediately make the work available online to all at no cost. (Jill Cirasella)
Green OA: Refers to materials that, regardless of where else they appear, are made available at no charge in an online open acces repository committed to long-term preservation. Journals are called "green" if they permit authors to self-archive their articles in OA repositories. (Jill Cirasella)
Hybrid Journals: These are journals that support open access and are basically two journals in one: a subscription journal and an open access journal. After acceptance you can choose how you wish to publish your article. (Elsevier)
Impact Factor: “Average number of times articles from the journal published in the past two years have been cited in the JCR year” (JCR glossary).
In other words, it is a measure of a journal’s relative importance in a subject category, and a legitimate source for impact factors is Thomson Reuters’ Journal Citation Reports®
Open Access (OA) Literature: Barrier-free access to online works and other resources. OA literature is digital, online, free of charge, and free of needless copyright and licensing restrictions. (Peter Suber)
Here are places to start your search for quality OA journals: