“Public access” is a term often used by federal funding agencies mandating that research results, including data, from projects they have funded be made publicly available within a certain time frame according to the terms of the agency's policy.
The National Institutes of Health (NIH) Public Access Policy requires that all peer-reviewed publications arising from NIH-funded research must be submitted to the digital archive PubMed Central upon acceptance for publication. The Policy requires that these papers are accessible to the public in PubMed Central no later than 12 months after publication.
A few thousand journals have agreements to deposit the final published versions of some or all of their articles directly in PMC. Use the PubMed Central Submission Process page to determine the requirements for your paper.