What is Open Access Publishing?

Open access (OA) literature is digital, online, free of charge, and free of most copyright and licensing restrictions.

There are two ways to open access - the golden and the green way. Also hybrid and delayed open access are used.

Golden OA imply that the article is immediately freely available on the journal's website when published. The journal is OA in its entirety, which means that all articles are freely available. In some cases there is a fee involved, a so-called Article Processing Charge, APC.
Green OA imply that a copy of an article published in the traditional way, is deposited in an institutional repository or in a subject repository. This paralell published article can be a pre-print version (submitted), a post-print version (accepted), or a published version.
Hybrid OA is an immediately freely available article, published on a website of a traditional publisher. This means that the author has paid a fee in order to make the article freely available.
Delayed OA is an article published in the traditional way, which the publisher makes freely available on the journal's website after an embargo period of up to two years.

The biggest advantage of publishing open access is the fact that the article will reach a bigger audience since it will be freely available. More researchers can pursue the idea and the author will get more citations. Also non-academic readers will get the opportunity to get in touch with accurate research

Exemples of open access sources:

DOAJ - Directory of Open Access Journals
Directory of over 5000 peer-reviewed journals, freely available online.
OpenDOAR -The Directory of Open Access Repositories
Directory of over 1500 open, digital repositories.
OpenAIRE
European digital repositories.
DiVA-portal
Digital repository of Swedish universities and one Norwegian.
OAIster
Over 30 millions freely available digital resources.
PLOS - Public Library of Science
A nonprofit publisher and advocacy organization founded to accelerate progress in science and medicine by leading a transformation in research communication.