Open access journals mean that readers don’t pay for accessing research papers.

These papers are usually peer-reviewed prior to publication

Examples of open access journals:

BMJ www.bmj.com (BMA pays)

BiomedCentral www.biomedcentral.com (author pays processing fee, readers don’t pay)

Smaller independent journals e.g.
J Med Internet Res www.jmir.org (run by researchers independently from publishers)

PubMedCentral www.pubmedcentral.gov (aggregator of online journals, papers become available after 1 year)