Because all original work published to the Internet is automatically covered by copyright laws, there needed to be a middle ground. Some people simply wish to share their work on the Web and do not want to bother with claims for copyright. For this reason, the Creative Commons was created as an alternative to making claims for complete copyright protection. It is important to understand that copyright laws only protect your original work, if you copy some other work or incorporate it in your publication, you may be violating someone's copyright claim.
The Creative Commons (CC) is a non-profit organization founded in 2001 dedicated to expanding the legal rights normally restricted by copyright law. Over time, CC has created innovative copyright licenses called Creative Commons Licenses, which provide a reasonable flexible alternative to asserting a claim to a full copyright.
The various CC Licenses enable those who create works, especially for publication on the Internet, with a means to reserve those rights they wish to preserve and waive other specifically defined rights for the benefit of the users. As described by Wikipedia, CC replaces “individual negotiations for specific rights between copyright owner (licensor) and licensee, which are necessary under an "all rights reserved" copyright management with a "some rights reserved" management employing standardized licenses for re-use cases where no commercial compensation is sought by the copyright owner. The result is an agile, low overhead and cost copyright management regime, profiting both copyright owners and licensees. Wikipediais using one of its licenses.” 
Simply put, the Creative Commons provides a standardized way to give the public permission to use your original work, without losing your basic copyright claims, on conditions of your choice. This is done through a series of copyright licenses designed to give different levels of permission. The licenses are designed to ensure that the owner of the copyright gets credit for their work.
Before you can choose to use a Creative Commons license, there are some concepts you need to understand. First, is the concept of a license. When you own a copyright to an original work, you can enter into a contract to sell or license that ownership right. If you license the right, you are not selling all of your interest, just a portion of it based on the conditions contained in the license. If you allowed others to copy your work without defining your interest, you risk losing your copyright. So, allowing copies of your work subject to a license, helps you preserve your basic rights.
The Creative Commons has designed three layers of protection for its licenses; a legal code layer, a human readable layer and a machine readable layer. This is explained by the following quote from the Creative Commons website:
Our public copyright licenses incorporate a unique and innovative “three-layer” design. Each license begins as a traditional legal tool, in the kind of language and text formats that most lawyers know and love. We call this the Legal Code layer of each license. But since most creators, educators, and scientists are not in fact lawyers, we also make the licenses available in a format that normal people can read — the Commons Deed (also known as the “human readable” version of the license). The Commons Deed is a handy reference for licensors and licensees, summarizing and expressing some of the most important terms and conditions. Think of the Commons Deed as a user-friendly interface to the Legal Code beneath, although the Deed itself is not a license, and its contents are not part of the Legal Code itself. The final layer of the license design recognizes that software, from search engines to office productivity to music editing, plays an enormous role in the creation, copying, discovery, and distribution of works. In order to make it easy for the Web to know when a work is available under a Creative Commons license, we provide a “machine readable” version of the license — a summary of the key freedoms and obligations written into a format that software systems, search engines, and other kinds of technology can understand. We developed a standardized way to describe licenses that software can understand called CC Rights Expression Language (CC REL) to accomplish this.Before trying to use a Creative Commons license, it is important to understand each of the six different license levels. The levels include decisions based on attribution, derivation, commercial vs. noncommercial and share alike. Attribution is a requirement that anyone who uses your content must give you credit. The basic Creative Commons license requires only attribution. Derivation means using your content to create another work that includes your original work as long as it is passed along unchanged and in whole, with credit to you. The other levels of Creative Commons licenses add restrictions on commercial use and restrict usage to situations where your original license is not made available in a less restrictive manner. This is called ShareAlike. Creative Commons licenses are valuable tools for anyone who publishes their original work on the Internet and it is important to understand these options.
 Wikipedia:Creative Commons, http://en.wikipedia.org/wiki/Creative_Commons, accessed 1 September 2012.  Wikipedia:Creative Commons, http://en.wikipedia.org/wiki/Creative_Commons, accessed 1 September 2012.  Creative Commons, About Licenses, http://creativecommons.org/licenses/, accessed 1 September 2012.