Open access journals can be defined as "journals that use a funding model that does not charge readers or their institutions for access" (Directory of Open Access Journals, 2012).
As access to online journal content becomes increasingly expensive, a widening gap occurs between what the journals cost, and what university libraries can pay. The open access model represents an alternative to the for-profit journal publishing model.
Open access journals are often high quality and many are peer-reviewed. Additionally, studies have shown that publishing in open access journals can increase citations to your article.
Read more about the benefits of open access here.