What is Attribution?

Legal Definition
Attribution in copyright law, is acknowledgement as credit to the copyright holder of a work. The most fundamental form of attribution is the statement of the copyright holder's identity, often in the form Copyright © [year] [copyright holder’s name]. The preservation of such a notice is invariably required until and unless a work has entered the public domain. Author attribution beyond such a notice is sometimes required by licenses, such as the GNU Free Documentation License and Creative Commons licenses.

Attribution is often considered as the most basic requirements made by a license, as it prevents others from claiming fraudulently to own the work and allows a copyright holder to accumulate a positive reputation that partially repays their losses. In cases when copyright holder is author himself it is regarded as a sign of decency and respect to acknowledge the creator by giving him/her credit for the work.
-- Wikipedia
Legal Definition
Labeling something as either the cause or effect of another item.