...online academic journals containing scholarly articles that are free for anyone to read, and whose contents are openly-licensed.

Because open access journals do not charge money to anyone to read them, yet still require some income to maintain (not as much as a print journal, of course), they often charge the authors who are being published a fee called an 'article processing charge' (APC), funding which pays for editing, the cost of renewing the website's registration, server space, etc. This fee may be paid by authors, their institution, or grant funding. The APC means that in OA journals, you pay to publish, instead of paying to read.

And yes, if a researcher has access to less financial support, they may find it harder to pay the APC to publish in an OA journal, especially the older, more well-known journals that include OA articles (and much higher APCs). This can and does leave researchers from less advantaged institutions, including those in less wealthy nations, less able to publish and be part of the scientific conversations in their field.

Some online academic journals were created to be open access from the very beginning, but others were more traditional ('pay to read') journals from before the internet, many of which now publish a combination of subscription articles AND open access articles in each issue. In this arguably complicated and confusing publishing model, these are known as 'hybrid' journals.

Not every online journal labeling itself as 'open access' is a fully legitimate journal.  Some online journals, known as 'predatory journals', will publish an author's article, take an article processing charge as payment, yet not properly edit or have that article peer-reviewed. In effect, they're a type of scammer, and having your work 'published' by a predatory journal can cost you money, time, and could cause damage to your professional reputation.

How can you best protect yourself from predatory journals?  Help is available on the following websites:

Think. Check. Submit.

• This site contains resources, such as checklists, to help academics Identify trusted publishers for their research.

"Predatory Journals: What They Are and How to Avoid Them"

• Article with good, general information.

GOLD OA

• Article published in an OA journal
• Article free to read immediately
• An article processing charge (APC) usually needs to be paid to the OA publisher

HYBRID OA

• Article published in a journal that contains both subscription (pay to read) and OA (pay to publish) articles
• An APC needs to be paid to the publisher
• The OA article is free to read immediately

GREEN OA

• Article is published / archived in an open repository
• Articles could theoretically be published here without having been published in any journal - though that might mean that no editing or peer review has been done.
• Some open repositories may permit the public to carry out open peer review of articles stored there via public comment
• If the article is also published in a subscription or hybrid journal, may not be able to be archived until after an embargo period / publishing delay has passed
• Article may be a pre-print (version before peer review and/or editing) or final, 'version of record' that appeared in a journal - depends on the terms of the publishing agreement if published first in a subscription/hybrid journal

Try Sherpa Romeo, an online resource that aggregates and analyses publisher open access policies from around the world and provides summaries of publisher copyright and open access archiving policies on a journal-by-journal basis. Search by journal title, issn, or publisher name.