Gold OA - Publishing in Open Access journals
In pure Open Access journals all the articles are openly accessible immediately without any embargo. Generally, authors maintain copyright and publications are accessible with an open licence.
Please note: Several journals/publishers use the term Gold OA about what is actually hybrid OA (se information on hybrid OA below).
Check www.doaj.org to see if a journal is Gold OA, as the majority of Gold OA journals are listed there.
Green OA - Self-archiving in Open repositories
Archiving scholarly articles, Master theses, PhD dissertations and other research materials in Open repositories ensures Open Access. Generally, scholarly articles may be deposited in a postprint or accepted manuscript version (AAM). This version is the last version that the author submits, post-peer review, and differs in format but not contents from the final, published version. Often, publishers or journals require an embargo of 6 to 36 months upon publication before post-prints may be made available. See instructions on how to self-archive your articles.
Hybrid OA - Open publishing in subscription-based journals
Hybrid OA implies paying for Open Access for individual articles. These articles are published in traditionally subscription-based journals but are made openly accessible through payment of a publication fee (APC). Generally, hybrid OA is the most expensive way of achieving Open Access.