Open Access (OA) refers to research outputs that are freely available on the internet for all to read. Open Access widens access to peer-reviewed scholarly information beyond the people who have access to subscription titles to the general public, increasing the impact of research beyond the university.
The level of "openness" is generally more obvious if the author has applied a Creative Commons license to their online material.
Tied up with open access is the fact that many publishers ask researchers to transfer copyright of their research outputs to the researcher, thereby restricting how researchers can re-use their outputs.
The following are some of the various models currently being used by which researchers can reuse their outputs: