Open access typically refers to journal articles and monographs that are published under an open license and are available for anyone to access and reuse, without paywalls, logins, or other barriers to access. Sometimes you might find copyrighted content that is free to read online, but this content is not openly licensed and may not be reused without permission. By removing barriers to access, OA publishing makes your work more visible. This increased visibility leads to an increase in downloads and citations of OA articles compared to those published by subscription journals. People all over the world are able to read your research, freely share it with others, build on what you have written, and create networks of academics doing similar work.
Creative Commons (CC) is a non-profit organization and international network devoted to educational access and expanding the range of creative works available for others to build upon legally and to share. The organization has released several licenses that allow authors of creative works to communicate which rights they reserve and which rights they waive for the benefit of recipients or other creators. Content owners still maintain their copyright, but Creative Commons licenses give standard releases that replace the individual negotiations for specific rights between copyright owner (licensor) and licensee, that are necessary under an "all rights reserved" copyright management. More information can be found on this guide.
Learn more about sharing your work and picking a license. The FAQ page can help you determine how to combine material under different CC licenses, which CC licenses you can use or apply to derived or adapted material, compliance with licenses, and much more.