Open Access wants to achieve free availability and reusability of digital scientific information, particularly with regard to scholarly publications.
Free availability and reusability imply that publications are available without barriers – i.e. without technical, legal or financial restrictions –, and that everybody should be able to read, copy, print and distribute them within the options of copyright law. Publishing under a Creative Commons license creates legal certainty for open access publications.
Gold Road Open Access
Golden road open access means that publications are open access from the moment of their being published. Open access in this case is the original form of publication. This can be in fully open access journals or on repositories.
Green Open Access
With the Green Road, the paper is originally published behind a paywall, f. e. in a subscription journal. Only after the expiry of a period of embargo, can the publication then be made available in open access on a repository. This type is therefore called second publication or self-archiving.