When your article is reviewed and accepted for publication, you will typically be asked to sign a standard agreement that transfers most (if not all) of your rights to the publisher. This makes them the copyright holder of your work and limits what you can do with it going forward. As an author, you have the following rights unless you transfer the copyright in a signed agreement:
Publishers will require certain rights. For instance, they cannot distribute your work unless you give them that right. However, you do not necessarily have to sign over all of your rights. And you should be wary and carefully read any agreement. Some agreements can limit your ability to store your work in a repository or even to re-use your data in future publications.
It's important to note that a publisher may be willing to negotiate terms. You can correspond with them and try to negotiate for certain allowances, if you don't like the agreement that's offered.
The moment you create it in a "tangible form", whether published or not, you have copyright over that work. No one else may copy, distribute, or perform your work without your permission.
Creative Commons licenses are free copyright licenses that creators can use to indicate how they'd like their work to be used. Creators can choose from a set of licenses with varying permissions, from the most open license (CC0) to the least open license (CC BY-NC-ND). The license most commonly used by educators tends to be the CC BY license (can distribute, remix, and adapt so long as you give credit).
See list and image below for the range of licenses. Click on each license name for a complete description of the terms & uses of each CC license.
Image sourced from foter.com, CC BY-SA
BY stands for attribution. It means you must provide proper attribution to the creator when reusing or editing their materials.
SA means sharealike. It means that if you reuse their information or materials you must share it using the same Creative Commons license.
ND means no derivatives. It means you cannot edit or alter their resource. You can distribute it.
NC means no commercial use. It means you cannot sell or financially profit from their information/resource.
Image sourced from foter.com, CC BY-SA
Open Access Journals are a great resource for information and scholarship. Making information more freely accessible is a noble goal and publishing works in OA journals is a great way to contribute. There are, however, complications to consider such as reputation of the journal and sustainability. Some OA journals will require payments to publish in them, as that is how they fund the work that goes into maintaining them. Payment should not, however, even guarantee publication. If payment ensures publication or improves your chances, you're most likely dealing with a predatory journal.
There are benefits to publishing in an OA journal. Besides supporting free and affordable research, publishing in an OA journal can result in a wider readership for your article! Rather than having your work locked behind a pay wall, any scholars can access and view your work.