Holders of the copyright on creative works have the absolute power to license others to make specific uses of their work. A copyright holder may, for example, declare the work to be in the public domain, and relinquish copyright altogether Or, the copyright holder can grant specific rights to specific individuals, groups or corporations.
Creative Commons (https://creativecommons.org/) is an international non-profit organization that has created legal language to allow authors/creators to grant selected rights to users automatically, while retaining your copyright.
The Creative Commons website lets you select the nation in which you have copyright, then the permissions you want to grant, and generates a license you can attach to your copyrighted work.
BY - Credit must be given to the creator
NC - Only non-commercial uses permitted
SA - Adaptations must be shared under the same terms
ND - No derivatives or adaptations permitted
There is also a CC 0, or public domain declaration option.
Note Once a CC license is applied to a work, it cannot be changed or revoked.
CC licenses can only be applied by the owner or controller of the copyright.
The license must be displayed in the work, along with a link to the text of the license. This may be either done in text, with a link to the Creative Commons full license.