The Creative Commons licenses are made up of three distinct parts, which serve to provide information to different groups.
The first part is the legal code, which is the language that is needed to give the licenses strength and legal legitimacy. In the unlikely case that a copyrighted work with CC licensing ends up in court, this legal code is the language at which the court will be looking to ensure that the CC licenses was followed. To see the strength of the language, use this link to view the CC BY legal code.
The second part of the licenses are known as the common deeds. This part is the language that we all think of when we think off CC licenses: CC BY, SA, NC, etc. These common deeds are essentially shortcuts to the legal code discussed above. If you license your work with a CC BY license, that is backed up by legal language but the public recognizes these common deeds
The third part of a Creative Commons license is essentially a machine-readable format of the common deeds. This machine readable code allows search engines to search on a specific level of CC licensing, ensuring that the person doing the searching will find information that can be used for their level of need.