Creative Commons licenses build on copyright. By applying a Creative Commons license, "creators grant permission toe everyone in the world to use their work in certain ways."
You can use CC-licensed materials as long as you follow the license conditions. One condition of all CC licenses is attribution.
Including attribution, a CC license combines four conditions to determine one of six types of license which come in three formats.
Most Open Educational Resources (OER) use Creative Commons licenses or some other type of open license. Some are in the public domain. Make sure to check for licensing restrictions, as well as OER's that use fully copyrighted works without permission.