Another option authors have for specifying how work may be reused is through a license. Some publishers offer their own license, but a Creative Commons license may also be appropriate. The six Creative Commons license options define terms and expectations between the copyright owner and user. Once selected, the desired license is sent to the author by Creative Commons in HTML and can be added to the copyright owner's website or hosting service if the service has incorporated Creative Commons. 

Popular Creative Commons Licenses include

CC BY Creative Commons Attribution:   

Works shared under this license are known as attribution only.  This means that you retain authorship rights over your work but others can use and reuse your work however they want.  

CC BY-SA  Creative Commons Attribution ShareAlike: 

Works shared under this license are not only attributed to the author, but are also shared under the same terms.  That is, the work is attributed to the original author(s), and creators of derivative items and future works must be shared similarly.  This does not prevent commercial use of your work.