Wikipedia is not an authoritative source regarding Creative Commons, but it does have historically useful information. CC does have a thing called Public Domain Mark 1.0, which asserts
This work has been identified as being free of known restrictions
under copyright law, including all related and neighboring rights. You
can copy, modify, distribute and perform the work, even for commercial
purposes, all without asking permission.
The thing they call CC0, labeled "Public Domain Dedication" provides a slightly different legal assertion
The person who associated a work with this deed has dedicated the work
to the public domain by waiving all of his or her rights to the work
worldwide under copyright law, including all related and neighboring
rights, to the extent allowed by law. You can copy, modify, distribute
and perform the work, even for commercial purposes, all without asking
The two differ (at this level of comparison) in that the former says that there was no right at all (this "license" is simply information), and the latter (CC0 version 1) says that the rights in the work have been waived – to the extent allowed by law. The "legal code" is more verbose: it enumerates the protections that the rights-holder "hereby overtly, fully, permanently, irrevocably and unconditionally waives, abandons, and surrenders". The license also says that in case it is determined that some part of the wording that waives rights is deemed to be no good, then the rights-holder grants a very unrestrictive license. The CC Wiki take on the distinction is here, and basically says that it has to do with "is already free of restriction" versus "is hereby dedicated to the public domain". An example would be a work of the US government, the IRS's instruction booklet for income taxes, which are automatically in the public domain per 17 USC 105 (although "public domain" is not a term in the copyright statutes, which say that protection is not avilable).