Sometimes creators will assign an open license to their work. An open license grants other creatives permission to use a work as long as they follow certain guidelines, usually attributing the work to the original creator at minimum. Openly licensed works are meant to be shared, remixed, and built upon. Looking at the details of the license will let you know exactly what you can and can't do with a work, and what rules (like attribution) need to be followed. Many websites are dedicated to sharing openly licensed materials.
Creative Commons (CC) licenses are open licenses that allow creators to retain the copyright to their original work while also allowing the public to use that work without asking for permission as long as they follow certain guidelines, like attributing the work to the original creator. There are six different CC licenses, and each license explains very clearly what you can or cannot do with a piece of work. For instance, a license will clearly state whether or not you can use the original work for commercial purposes.
You may come across language you are unfamiliar with while looking at CC licenses. Or the language might be familiar, but you're curious exactly what it means in this legal context. Below are some important terms to understand in order to feel confident that you are legally using CC licensed work.
Distribute: To hand out, perform, play, or display the work in any manner - including online.
Remix: To edit and adapt a work in any way. You're probably most familiar with this term in the context of music, but you can remix a painting, video, or written work as well. It's adding your own flair to the original work.
Build Upon: To take a work and expand it. You're probably most familiar with this as fanfiction or as adaptions of classics like Sherlock Holmes and Pride and Prejudice. These are often called derivatives or adaptations.
No Derivatives: The work should not be edited or adapted in any way. It must be used in its original format.
Commercial Use: The work is being used in a way that will make you a profit. Something important to consider when posting CC content online is that if you post a work (even a remixed work) on a social media platform that you have sponsored material on, or that you commonly link back to your patreon, that could be interpreted as commercial use, especially if you have a large following. In that case, you would need to make sure you are using CC content that allows for commercial use in the license.
Attribution: Credit to the original creator. In the context of CC, this means following proper attribution guidelines (found on the citing or attributing tab), not just sharing the creator's name or a link.