Open access is the practice of allowing everyone free and unrestricted access to certain full-text journals, books, software and courseware via the Internet.
Open Access and Open Content are not the same, since many Open Access resources are restricted in that they cannot be edited in any way.
Open Content is the practice used by sites such as Wikipedia, or with materials having Creative Commons Licensing, that allows anyone to edit the work, adding additional information, corrections or deleting portions of a work.
Open-Source is the term used with software, when a software is licensed to allow programmers to change and distribute it. See this GNU Licensing link
