Open access is about making scholarly information available online, unrestricted and free. In addition to research articles, open access documents can include open data, science, open books and textbooks, and open education. Open access frees research so that it is disseminated faster, and worldwide, supporting advancement in discovery and knowledge.
Gold Open Access: Gold OA means that the work (final version) is freely available and accessible to everyone, immediately after publication. A Gold OA option can be achieved by publishing your work in fully open access journals, or in a hybrid model, where a subscription based publisher offers the Gold OA option for a fee.
Green Open Access: Green OA, also called self-archiving, is where authors can post a version of their work into an OA repository, making it freely accessible to everyone. The "version" of the article that can be deposited is dependent on the funder or publisher. For example, the Journal of Nursing Management allows author to deposit their pre-print (1st draft sent to publisher) in their institutional repository, or, the post-print version (final proof/last version before official publication) in their institutional repository--but not the final PDF manuscript. Often, the green OA option comes with particular conditions like an embargo period (usually 12-24 months), requirements to link to the publisher's version, and more.
To find out the open access policies of journals you have published in, try searching for the journal in SHERPA/RoMEO.
Pre-print version: The version of an article before peer-review. This version may include draft versions, works in progress and submitted versions to a journal for peer-review.
Post-print version: Final, accepted, peer-reviewed version of an article, before the publisher’s layout and typesetting is applied; (also known as accepted version or final author manuscript).
Creative video defining open access and what it's all about, from PHD Comics.