Creative Commons licenses are special copyright licenses that have been developed by the Creative Commons (CC) non-profit organization to promote the free and open use of creative works. You can apply a CC license to anything you create to allow others to use it (while enabling you to keep the main copyright).

You can access their "Choose a license" site here to read about the licenses.
The main license types are described here: https://creativecommons.org/share-your-work/cclicenses/

Image source: Creative Commons (CC0)